We need to generate string literals. Best to use a quote function
instead of concatenating on quote marks withou escaping. Copy a
well-tested one from Code City.
* Terminology change: use "compressed" and "uncompressed" to describe
what Closure Compiler calls "compiled" and "uncompiled", to reduce
confusion with the compilation that will be done by tsc.
* Get the list of modules to bootstrap (in compressed mode), or
scripts to load (in compressed mode) from BLOCKLY_BOOTSTRAP_OPTIONS,
to allow calling scripts to to specify exactly what to load.
Previously the (non-advanced) playground was only correctly loadging
on localhost because you can put an arbitrary number of "../"s in front
of a relative URL and it just takes you to the root directory.
Since prepare.js and blockly.mjs are going to be needed for running
all tests in uncompiled mode (not just the playgrounds), move them
tests/. Further, rename prepare.js to bootstrap.js to better reflect
its purpose.
