show error when loading plugin defnitions failed

src/client/js/plugin.js

@@ -1,3 +1,7 @@
+import loggerFactory from '@alias/logger';
+
+const logger = loggerFactory('growi:plugin');
+
 export default class CrowiPlugin {
 
   /**
@@ -15,8 +19,8 @@ export default class CrowiPlugin {
       definitions = require('@tmp/plugins/plugin-definitions');
     }
     catch (e) {
-      // TODO show warning
-      // do nothing
+      logger.error('failed to load definitions');
+      logger.error(e);
       return;
     }