feat(build): Have npm scripts run npm ci first where applicable

Have any npm script that have external effects (e.g. publishing an
npm package, pushing a new version to appengine, or updating GitHub
Pages) start by running npm ci to ensure that all dependencies are
up-to-date with respect to package-lock.json.

(This is done by npm and not a gulp script because gulp itself
might need updating.  So might npm, but that is less likely to
make any difference to what gets published/pushed.)

package.json

@@ -32,8 +32,8 @@
     "clean:build": "gulp cleanBuildDir",
     "clean:release": "gulp cleanReleaseDir",
     "checkin": "gulp checkin",
-    "deployDemos": "gulp deployDemos",
-    "deployDemos:beta": "gulp deployDemosBeta",
+    "deployDemos": "npm ci && gulp deployDemos",
+    "deployDemos:beta": "npm ci && gulp deployDemosBeta",
     "format": "gulp format",
     "format:sortrequires": "gulp sortRequires",
     "generate:langfiles": "gulp generateLangfiles",
@@ -44,8 +44,8 @@
     "package": "gulp package",
     "prepare": "gulp prepare",
     "prepareDemos": "gulp prepareDemos",
-    "publish": "gulp publish",
-    "publish:beta": "gulp publishBeta",
+    "publish": "npm ci && gulp publish",
+    "publish:beta": "npm ci && gulp publishBeta",
     "recompile": "gulp recompile",
     "release": "gulp gitCreateRC",
     "start": "http-server ./ -o /tests/playground.html -c-1",
@@ -53,7 +53,7 @@
     "test:generators": "tests/scripts/run_generators.sh",
     "test:mocha:interactive": "http-server ./ -o /tests/mocha/index.html -c-1",
     "test:compile:advanced": "gulp buildAdvancedCompilationTest --debug",
-    "updateGithubPages": "gulp gitUpdateGithubPages"
+    "updateGithubPages": "npm ci && gulp gitUpdateGithubPages"
   },
   "main": "./index.js",
   "umd": "./blockly.min.js",