add a bugs entry in package.json

Author: d-biehl

package.json

@@ -7,7 +7,10 @@
   "version": "0.2.2",
   "repository": {
     "type": "git",
-    "url": "https://github.com/d-biehl/robotcode.git"
+    "url": "https://github.com/d-biehl/robotcode"
+  },
+  "bugs": {
+    "url": "https://github.com/d-biehl/robotcode/issues"
   },
   "engines": {
     "vscode": "^1.60.0"