Restore extensions in core (#114921)

* bring back grammar extensions

* fix hygiene

* Revert "pull themes from the marketplace"

This reverts commit 0738f76dac.

extensions/fsharp/package.json

@@ -0,0 +1,29 @@
+{
+	"name": "fsharp",
+	"displayName": "%displayName%",
+	"description": "%description%",
+	"version": "1.0.0",
+	"publisher": "vscode",
+	"license": "MIT",
+	"engines": { "vscode": "*" },
+	"scripts": {
+		"update-grammar": "node ../../build/npm/update-grammar.js ionide/ionide-fsgrammar grammars/fsharp.json ./syntaxes/fsharp.tmLanguage.json"
+	},
+	"contributes": {
+		"languages": [{
+			"id": "fsharp",
+			"extensions": [ ".fs", ".fsi", ".fsx", ".fsscript" ],
+			"aliases": [ "F#", "FSharp", "fsharp" ],
+			"configuration": "./language-configuration.json"
+		}],
+		"grammars": [{
+			"language": "fsharp",
+			"scopeName": "source.fsharp",
+			"path": "./syntaxes/fsharp.tmLanguage.json"
+		}],
+		"snippets": [{
+			"language": "fsharp",
+			"path": "./snippets/fsharp.code-snippets"
+		}]
+	}
+}