tweak eslint rules a bit more

add angular as global
add no-var rule
add prefer-const rule

.eslintrc.json

@@ -1,6 +1,11 @@
 {
-    "extends": "standard",
-    "rules": {
-        "semi": "off"
-    }
+  "extends": "standard",
+  "globals": {
+    "angular": "readonly"
+  },
+  "rules": {
+    "semi": ["error", "always"],
+    "no-var": "error",
+    "prefer-const": "error"
+  }
 }