Create .github folder and add pull request template and issue template (#1314)

* Create .github folder and move CONTRIBUTING.md to the new folder

* Add pull request template and issue template

* Update ISSUE_TEMPLATE.md

* Update PULL_REQUEST_TEMPLATE.md

* Update ISSUE_TEMPLATE.md

* Update PULL_REQUEST_TEMPLATE.md

.github/CONTRIBUTING.md

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+# Contributing to Blockly
+
+Want to contribute? Great!
+- First, read this page (including the small print at the end).
+- Second, please make pull requests against develop, not master. If your patch
+  needs to go into master immediately, include a note in your PR.
+
+For more information on style guide and other details, head over to the [Blockly Developers site](https://developers.google.com/blockly/guides/modify/contributing).
+
+### Before you contribute
+Before we can use your code, you must sign the
+[Google Individual Contributor License Agreement](https://cla.developers.google.com/about/google-individual)
+(CLA), which you can do online. The CLA is necessary mainly because you own the
+copyright to your changes, even after your contribution becomes part of our
+codebase, so we need your permission to use and distribute your code. We also
+need to be sure of various other things—for instance that you'll tell us if you
+know that your code infringes on other people's patents. You don't have to sign
+the CLA until after you've submitted your code for review and a member has
+approved it, but you must do it before we can put your code into our codebase.
+
+### Larger changes
+Before you start working on a larger contribution, you should get in touch with
+us first through the issue tracker with your idea so that we can help out and
+possibly guide you. Coordinating up front makes it much easier to avoid
+frustration later on.
+
+### Code reviews
+All submissions, including submissions by project members, require review. We
+use Github pull requests for this purpose.
+
+### Browser compatibility
+We care strongly about making Blockly work on all browsers.  As of 2017 we 
+support IE 10 and 11, Edge, Chrome, Safari, and Firefox.  We will not accept
+changes that only work on a subset of those browsers.  You can check [caniuse.com](https://caniuse.com/) 
+for compatibility information.
+
+### The small print
+Contributions made by corporations are covered by a different agreement than
+the one above, the
+[Software Grant and Corporate Contributor License Agreement](https://cla.developers.google.com/about/google-corporate).

.github/ISSUE_TEMPLATE.md

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+Thanks for opening an issue for us!  Before you open an issue, please check if a similar issue exists or has been closed before.
+
+If you're asking a question about how to use Blockly in your application, please ask questions on the [mailing list](https://groups.google.com/forum/#!forum/blockly) instead of filing issues.
+
+_Please delete the above section and the instructions in the sections below before submitting.  If a section is not applicable, type "N/A" in that section._
+
+### Problem statement
+
+_Remove this hint: these checkboxes can be checked like this: [x]_
+
+- [ ] Bug report
+- [ ] Feature request
+
+_What were you trying to do when you hit this bug?  Or, what do you want to do with Blockly that your proposed feature would enable?_
+
+### Expected Behavior
+
+_Please describe what should happen.  Include screenshots if applicable._
+
+### Actual Behavior
+
+_Describe what actually happens.  Include screenshots if applicable._
+
+### Steps to Reproduce
+
+_Explain what someone needs to do in order to see what's described in *Actual behavior* above_
+
+### Stack Traces
+
+```
+Please open up the console.  If you see any Blockly-related errors, paste them here.
+
+Ignore any instances of "Uncaught (in promise) DOMException: The play() request was interrupted by a call to pause()."
+```
+
+### Operating System and Browser
+
+_Remove this hint: these checkboxes can be checked like this: [x]_
+
+- [ ] Desktop:
+  - [ ] Chrome
+  - [ ] Firefox
+  - [ ] Safari
+  - [ ] Opera
+  - [ ] IE 10+
+  - [ ] IE 11
+  - [ ] EDGE
+
+- [ ] Smartphone/Tablet/Chromebook (please complete the following information):
+  - Device: [e.g. iPhone6]
+  - OS: [e.g. iOS8.1]
+  - Browser [e.g. stock browser, safari]
+  - Version [e.g. 22]
+
+### Additional Information
+
+_Anything else we should know?_

.github/PULL_REQUEST_TEMPLATE.md

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+Thanks for submitting code to Blockly!  Please fill out the following as part of your pull request so we can review your code more easily.
+
+## The basics
+
+- [ ] I branched from develop
+- [ ] My pull request is against develop
+- [ ] My code follows the [style guide](https://developers.google.com/blockly/guides/modify/web/style-guide)
+
+## The details
+### Resolves
+
+_What Github issue does this resolve (please include link)?_
+
+### Proposed Changes
+
+_Describe what this Pull Request does.  Include screenshots if applicable._
+
+### Reason for Changes
+
+_Explain why these changes should be made.  Include screenshots if applicable._
+
+### Test Coverage
+
+_Please show how you have added tests to cover your changes, or tell us how you tested it and on which platforms._
+
+Tested on:
+_Remove this hint: these checkboxes can be checked like this: [x]_
+- [ ] Desktop:
+  - [ ] Chrome
+  - [ ] Firefox
+  - [ ] Safari
+  - [ ] Opera
+  - [ ] IE 10+
+  - [ ] IE 11
+  - [ ] EDGE
+
+- [ ] Smartphone/Tablet/Chromebook (please complete the following information):
+  - Device: [e.g. iPhone6]
+  - OS: [e.g. iOS8.1]
+  - Browser [e.g. stock browser, safari]
+  - Version [e.g. 22]
+  
+### Additional Information
+
+_Anything else we should know?_