Migrate CI from travis-ci.com to GitHub Actions

.github/workflows/main.yml

@@ -0,0 +1,27 @@
+name: build
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build-nixos:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Build for supported platforms on NixOS
+        run: docker-compose run build-nixos
+  build-archlinux:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Build for supported platforms on Arch Linux
+        run: docker-compose run build-archlinux
+  build-ubuntu:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Build for supported platforms on Ubuntu
+        run: docker-compose run build-ubuntu