First cut github actions

.github/workflows/prototyping.yml

@@ -0,0 +1,39 @@
+name: prototyping
+
+on:
+  push:
+    branches:
+      - 'master'
+      - 'prototyping'
+    paths:
+      - 'prototyping/**'
+  pull_request:
+    paths:
+      - 'prototyping/**'
+
+jobs:
+  unix:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: install agda
+      run: sudo apt-get install -y agda
+    - name: cmake configure
+      run: cmake .
+    - name: cmake build luau-ast
+      run: cmake --build . --target Luau.Ast.CLI
+    - name: check examples
+      working-directory: prototyping
+      run: agda Examples.agda
+    - name: cabal install
+      working-directory: prototyping
+      run: cabal install --lib aeson scientific vector
+    - name: build PrettyPrinter
+      working-directory: prototyping
+      run: agda --compile PrettyPrinter.agda
+    - name: run smoketest
+      working-directory: prototyping
+      run: ../lua-ast Examples/SmokeTest.lua | ./PrettyPrinter > Examples/SmokeTestOutput.lua
+    - name: diff smoketest
+      working-directory: prototyping
+      run: diff Examples/SmokeTest.lua SmokeTestOutput.lua