src/options.json: add emitWarningsAsErrors option for validation

Author: Edwin Zhang

src/options.json

@@ -40,6 +40,9 @@
     },
     "sourceMap": {
       "type": [ "string", "boolean" ]
+    },
+    "emitWarningsAsErrors": {
+      "type": ["boolean"]
     }
   },
   "errorMessage": {
@@ -50,7 +53,8 @@
       "syntax": "should be {String|Object} (https://github.com/postcss/postcss-loader#syntax)",
       "stringifier": "should be {String|Object} (https://github.com/postcss/postcss-loader#stringifier)",
       "plugins": "should be {Array|Object|Function} (https://github.com/postcss/postcss-loader#plugins)",
-      "sourceMap": "should be {String|Boolean} (https://github.com/postcss/postcss-loader#sourcemap)"
+      "sourceMap": "should be {String|Boolean} (https://github.com/postcss/postcss-loader#sourcemap)",
+      "emitWarningsAsErrors": "should be {Boolean} (https://github.com/postcss/postcss-loader#emitWarningsAsError)"
     }
   },
   "additionalProperties": true