Add decimal parsing support (#11640)

* docs: add DecimalLiteral to AST spec

* add decimal support

* fix: throw invalid decimal on start

* add DecimalLiteral type definitions

* update parser typings

* add generator support

* add syntax-decimal plugin

* Add syntax-decimal to babel-standalone

* add syntax-decimal to missing plugin helpers

* fix incorrect test macro

packages/babel-standalone/scripts/pluginConfig.json

@@ -2,6 +2,7 @@
   "external-helpers",
   "syntax-async-generators",
   "syntax-class-properties",
+  "syntax-decimal",
   "syntax-decorators",
   "syntax-do-expressions",
   "syntax-export-default-from",