add onDebug activation

Author: DonJayamanne

package.json

@@ -44,6 +44,7 @@
     "Other"
   ],
   "activationEvents": [
+    "onDebug",
     "onLanguage:python",
     "onCommand:python.python-debug.startSession",
     "onCommand:python.execInTerminal",
@@ -1570,4 +1571,4 @@
     "vscode": "^1.0.3",
     "webpack": "^1.13.2"
   }
-}
+}