[scoped-custom-element-registry] Port to TypeScript (#561)

* Fix eslintignore sync

* Port to TypeScript

* Some non-type changes

* Apply suggestions from code review

Co-authored-by: Russell Bicknell <bicknellr@google.com>

* Add type for form state

* Give explicit types for Maps, Sets, WeakMaps

* Add some comments and readonly markers

* Update deps

* Fix two build issues

Some TypeScripts need resolve explicitly typed, and some closure compiler versions need the `whenDefined` method on our registry ponyfill quoted.

* Add comment about how the main file is a script not a module.

* Minor updates to comments.

---------

Co-authored-by: Russell Bicknell <bicknellr@google.com>
Co-authored-by: Peter Burns <rictic@google.com>

.eslintignore

@@ -40,3 +40,7 @@ packages/webcomponentsjs/src/unresolved.*
 packages/webcomponentsjs/custom-elements-es5-adapter.js
 packages/webcomponentsjs/webcomponents-bundle.d.ts
 packages/webcomponentsjs/webcomponents-bundle.js*
+
+packages/scoped-custom-element-registry/**/.wireit/
+packages/scoped-custom-element-registry/**/.tsbuildinfo
+packages/scoped-custom-element-registry/**/build/

.eslintignore-sync

@@ -1,2 +1,5 @@
 [local]
 .gitignore
+
+[relative]
+packages/*/{.gitignore,.eslintignore}

.prettierignore

@@ -42,6 +42,8 @@ packages/webcomponentsjs/webcomponents-bundle.d.ts
 packages/webcomponentsjs/webcomponents-bundle.js*
 
 packages/scoped-custom-element-registry/**/.wireit/
+packages/scoped-custom-element-registry/**/.tsbuildinfo
+packages/scoped-custom-element-registry/**/build/
 
 LICENSE
 packages/*/LICENSE.md

packages/scoped-custom-element-registry/.gitignore

@@ -1 +1,3 @@
 .wireit/
+.tsbuildinfo
+build/

packages/scoped-custom-element-registry/closure-flags.txt

@@ -3,8 +3,8 @@
 --language_in=STABLE
 --language_out=ECMASCRIPT5_STRICT
 --dependency_mode=PRUNE
---entry_point=./src/scoped-custom-element-registry.js
---js=./src/scoped-custom-element-registry.js
+--entry_point=./build/scoped-custom-element-registry.js
+--js=./build/scoped-custom-element-registry.js
 --js_output_file=./scoped-custom-element-registry.min.js
 --output_wrapper="(function(){
 %output%
@@ -14,4 +14,5 @@
 --assume_function_wrapper=true
 --rewrite_polyfills=false
 --create_source_map=./scoped-custom-element-registry.min.js.map
+--source_map_input="./build/scoped-custom-element-registry.js|./build/scoped-custom-element-registry.js.map"
 --source_map_include_content