Build front-end assets on CircleCI

This means we don't need a bogus "eslint-disable-next-line import/no-unresolved" directive when importing built CSS, which ends up breaking lint locally. Fixes #7177

.circleci/config.yml

@@ -41,6 +41,7 @@ jobs:
           paths:
             - ~/project/node_modules/
           key: node-v1-{{ .Branch }}-{{ checksum "package-lock.json" }}
+      - run: npm run build
       - run: npm run lint:js
       - run: npm run lint:css
       - run: npm run test:unit:coverage -- --runInBand

client/src/components/CommentApp/utils/storybook.tsx

@@ -20,8 +20,7 @@ import { defaultStrings } from '../main';
 
 import CommentComponent from '../components/Comment/index';
 
-// Requires Wagtail static to be built, so raises error on CI
-// eslint-disable-next-line import/no-unresolved
+// Requires Wagtail static to be built
 import '../../../../../wagtail/admin/static/wagtailadmin/css/core.css';
 
 export function RenderCommentsForStorybook({

client/src/components/Sidebar/Sidebar.stories.tsx

@@ -9,7 +9,6 @@ import { LinkMenuItemDefinition } from './menu/LinkMenuItem';
 import { SubMenuItemDefinition } from './menu/SubMenuItem';
 import { initFocusOutline } from '../../utils/focus';
 
-// eslint-disable-next-line import/no-unresolved
 import '../../../../wagtail/admin/static/wagtailadmin/css/sidebar.css';
 import { CustomBrandingModuleDefinition } from './modules/CustomBranding';