ci: add GitHub action

.github/workflows/main.yml

@@ -0,0 +1,27 @@
+name: CI
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  workflow_dispatch:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    container: archlinux:base-devel
+    steps:
+      - name: Prepare
+        run: |
+          pacman-key --init
+          pacman -Syu --noconfirm
+          pacman -S --noconfirm git meson glslang libcap wlroots \
+            sdl2 vulkan-headers libx11 libxcomposite libxrender libxres \
+            libxtst libxkbcommon libdrm libinput wayland-protocols \
+            xorg-xwayland
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive
+      - name: Build
+        run: |
+          meson build/
+          ninja -C build/