Add support for web extension

This feature is not officially supported yet. See microsoft/vscode#111043

Fixes #199

Author: nicolasstucki

package.json

@@ -8,6 +8,11 @@
     "engines": {
         "vscode": "^1.5.0"
     },
+    "extensionKind": [
+        "ui",
+        "workspace",
+        "web"
+    ],
     "homepage": "https://github.com/scala/vscode-scala-syntax/blob/master/README.md",
     "repository": {
         "type": "git",