Restore extensions in core (#114921)

* bring back grammar extensions

* fix hygiene

* Revert "pull themes from the marketplace"

This reverts commit 0738f76dac.

extensions/php/.vscode/tasks.json

@@ -0,0 +1,11 @@
+{
+	"version": "2.0.0",
+	"command": "npm",
+	"type": "shell",
+	"presentation": {
+		"reveal": "silent"
+	},
+	"args": ["run", "compile"],
+	"isBackground": true,
+	"problemMatcher": "$tsc-watch"
+}