feat: add new parser babel-ts to parse TypeScript syntaxes via Babel (#6400)

* feat: add new parser `babel-ts` to parse TypeScript syntaxes via Babel

* docs: document parser babel-ts

* chore: enable babel-ts in markdown and worker.js

* verify all TS tests against babel-ts except disabled by disableBabelTS

* support for TSDeclareMethod; fix abstract properties and methods

* fix embedded angular templates and styles

* fix TSImportType

* simplify babel options combinations

* fix method decorators

* fix ranges

* work around loc inconsistencies for SequenceExpression

* don't print trailing comma in type parameters (unsupported in TS < 3.3)

* preserve quotes for class properties

* align printing of single-parameter functions

* fix comments in degenerate single-element unions and intersections

* fix comments for methods

* fix comments for mapped types

* edit docs, change 'since' to 2.0.0

* add changelog

* fix code sample on playground

* update snapshots after rebase

Co-authored-by: Georgii Dolzhykov <thorn.mailbox@gmail.com>

website/playground/codeSamples.js

@@ -38,6 +38,7 @@ export default function(parser) {
         'declare type FetchPolicy = "cache-first" | "cache-and-network" | "network-only" | "cache-only"'
       ].join("\n");
     case "typescript":
+    case "babel-ts":
       return [
         "interface MyInterface {",
         "  foo(): string,",