DEV: Add linting workflow

.github/workflows/plugin-linting.yml

@@ -0,0 +1,41 @@
+name: Linting
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Node.js
+      uses: actions/setup-node@v1
+      with:
+        node-version: 12
+
+    - name: Set up ruby
+      uses: actions/setup-ruby@v1
+      with:
+        ruby-version: 2.7
+
+    - name: Setup bundler
+      run: gem install bundler -v 2.1.4 --no-doc
+
+    - name: Setup gems
+      run: bundle install --jobs 4
+
+    - name: Yarn install
+      run: yarn install --dev
+
+    - name: ESLint
+      run: yarn eslint --ext .js,.js.es6 --no-error-on-unmatched-pattern assets/javascripts
+
+    - name: Prettier
+      run: |
+        yarn prettier -v
+        yarn prettier --list-different \
+          "assets/**/*.{scss,js,es6}"
+
+    - name: Rubocop
+      run: bundle exec rubocop .