pluginloader: expose flot gauge plugin

public/app/features/plugins/plugin_loader.ts

@@ -126,6 +126,7 @@ import 'vendor/flot/jquery.flot.stackpercent';
 import 'vendor/flot/jquery.flot.fillbelow';
 import 'vendor/flot/jquery.flot.crosshair';
 import 'vendor/flot/jquery.flot.dashes';
+import 'vendor/flot/jquery.flot.gauge';
 
 const flotDeps = [
   'jquery.flot',
@@ -137,6 +138,7 @@ const flotDeps = [
   'jquery.flot.selection',
   'jquery.flot.stackpercent',
   'jquery.flot.events',
+  'jquery.flot.gauge',
 ];
 for (let flotDep of flotDeps) {
   exposeToPlugin(flotDep, { fakeDep: 1 });