feat(build): add e2e workflow

.github/workflows/e2e.yml

@@ -0,0 +1,31 @@
+name: e2e
+on: [ push ]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive
+      - name: Set up PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 7.4
+          tools: composer:v2
+      - name: Prepare the API
+        run: |
+          composer install --prefer-dist --no-interaction --no-scripts --no-progress
+          php artisan key:generate --quiet
+      - name: Set up Node
+        uses: actions/setup-node@v2
+        with:
+          node-version: 14
+      - name: Install submodule dependencies
+        working-directory: ./resources/assets
+        run: yarn install
+      - name: Build the client application
+        run: |
+          yarn install
+          yarn build --no-progress
+      - name: Run E2E tests
+        run: yarn test:e2e:ci

.github/workflows/unit.yml

@@ -1,4 +1,4 @@
-name: main
+name: unit
 on: [ push ]
 jobs:
   test:

README.md

@@ -1,4 +1,4 @@
-# koel [![GitHub Actions](https://github.com/koel/koel/workflows/main/badge.svg)](https://github.com/koel/koel/actions) ![Code Quality](https://scrutinizer-ci.com/g/phanan/koel/badges/quality-score.png?b=master) [![codecov](https://codecov.io/gh/koel/koel/branch/master/graph/badge.svg)](https://codecov.io/gh/koel/koel) [![OpenCollective](https://opencollective.com/koel/backers/badge.svg)](#backers) [![OpenCollective](https://opencollective.com/koel/sponsors/badge.svg)](#sponsors)
+# koel [![GitHub Actions](https://github.com/koel/koel/workflows/unit/badge.svg)](https://github.com/koel/koel/actions) ![Code Quality](https://scrutinizer-ci.com/g/phanan/koel/badges/quality-score.png?b=master) [![codecov](https://codecov.io/gh/koel/koel/branch/master/graph/badge.svg)](https://codecov.io/gh/koel/koel) [![OpenCollective](https://opencollective.com/koel/backers/badge.svg)](#backers) [![OpenCollective](https://opencollective.com/koel/sponsors/badge.svg)](#sponsors)
 
 ![Showcase](https://koel.dev/img/showcase.png)
 
@@ -21,9 +21,13 @@ Since Koel makes use of [git submodules](https://git-scm.com/book/en/v2/Git-Tool
 ```bash
 git pull
 git submodule update --init --recursive --remote
+
+# install the submodule dependencies
+cd resources/assets
+yarn install
 ```
 
-To start the **PHP dev server**, which serves as the API of the application, run the following command. By default, the server will listen at port `8000`.
+To start the **PHP dev server**, which serves as the API of the application, run the following command from the root directory. By default, the server will listen at port `8000`.
 
 ```bash
 php artisan serve