Added build workflow (pterodactyl#3963)

Author: mrxbox98

.github/workflows/build.yml

@@ -0,0 +1,24 @@
+name: Build Panel
+on:
+  push:
+    branches:
+      - 'develop'
+      - 'v2'
+  pull_request:
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+    if: "!contains(github.event.head_commit.message, 'skip ci') && !contains(github.event.head_commit.message, 'ci skip')"
+    strategy:
+      matrix:
+        node-version: [16.x]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v2
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'npm'
+    - run: npm install -g yarn
+    - run: yarn install
+    - run: yarn build:production