Use common form.js

app/assets/javascripts/dispatcher.js

@@ -310,12 +310,12 @@ import Activities from './activities';
             .catch(fail);
           break;
         case 'snippets:create':
-          import('./pages/snippets/create')
+          import('./pages/snippets/new')
             .then(callDefault)
             .catch(fail);
           break;
         case 'snippets:update':
-          import('./pages/snippets/update')
+          import('./pages/snippets/edit')
             .then(callDefault)
             .catch(fail);
           break;

app/assets/javascripts/pages/snippets/edit/index.js

-import GLForm from '~/gl_form';
-import ZenMode from '~/zen_mode';
-export default () => {
-  new GLForm($('.snippet-form'), false); // eslint-disable-line no-new
-  new ZenMode(); // eslint-disable-line no-new
-};
+import form from '../form';
+export default form;

app/assets/javascripts/pages/snippets/new/index.js

-import GLForm from '~/gl_form';
-import ZenMode from '~/zen_mode';
-export default () => {
-  new GLForm($('.snippet-form'), false); // eslint-disable-line no-new
-  new ZenMode(); // eslint-disable-line no-new
-};
+import form from '../form';
+export default form;

app/assets/javascripts/pages/snippets/update/index.js

-import GLForm from '~/gl_form';
-import ZenMode from '~/zen_mode';
-
-export default () => {
-  new GLForm($('.snippet-form'), false); // eslint-disable-line no-new
-  new ZenMode(); // eslint-disable-line no-new
-};