Migrate CI and packaging from Travis CI to GitHub Actions.

.github/workflows/ci.yaml

@@ -0,0 +1,48 @@
+name: Continuous Integration
+
+on:
+  push:
+  pull_request:
+    branches: [ bleed ]
+
+jobs:
+  linux-mono:
+    name: Linux (mono)
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Clone Repository
+        uses: actions/checkout@v2
+
+      - name: Check Code
+        run: |
+          mono --version
+          make check
+          mono ~/.nuget/packages/nunit.consolerunner/3.11.1/tools/nunit3-console.exe --noresult bin/OpenRA.Test.dll
+
+      - name: Check Mods
+        run: |
+          sudo apt-get install lua5.1
+          make check-scripts
+          make test
+
+  windows:
+    name: Windows (Framework 4.7)
+    runs-on: windows-2019
+
+    steps:
+      - name: Clone Repository
+        uses: actions/checkout@v2
+
+      - name: Check Code
+        shell: powershell
+        run: |
+          .\make.ps1 check
+          Invoke-Expression "$home\.nuget\packages\nunit.consolerunner\3.11.1\tools\nunit3-console.exe --noresult bin/OpenRA.Test.dll"
+
+      - name: Check Mods
+        run: |
+          chocolatey install lua --version 5.1.5.52
+          $ENV:Path = $ENV:Path + ";C:\Program Files (x86)\Lua\5.1\"
+          .\make.ps1 check-scripts
+          .\make.ps1 test