Replace Travis CI with Github workflow

.github/workflows/build.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+
+env:
+  CALCROM_DISCORD_WEBHOOK_USERNAME: ${{ secrets.CALCROM_DISCORD_WEBHOOK_USERNAME }}
+  CALCROM_DISCORD_WEBHOOK_AVATAR_URL: ${{ secrets.CALCROM_DISCORD_WEBHOOK_AVATAR_URL }}
+  CALCROM_DISCORD_WEBHOOK_URL: ${{ secrets.CALCROM_DISCORD_WEBHOOK_URL }}
+
+jobs:
+  build:
+    runs-on: ubuntu-18.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@master
+
+      - name: Install binutils
+        run: sudo apt install gcc-arm-none-eabi binutils-arm-none-eabi
+        # build-essential, git, and libpng-dev are already installed
+        # gcc-arm-none-eabi is only needed for the modern build
+        # as an alternative to dkP
+
+      - name: Install agbcc
+        run: |
+          git clone https://github.com/pret/agbcc.git
+          cd agbcc 
+          ./build.sh
+          ./install.sh ../
+
+      - name: Compare
+        run: make -j${nproc} compare
+
+      - name: Modern
+        run: make -j${nproc} modern
+
+      - name: Webhook
+        run: sh .github/calcrom/webhook.sh pokeemerald