add github action for continuous integration (#3)

Author: fblanqui

.github/workflows/main.yml

@@ -0,0 +1,30 @@
+on:
+  pull_request:
+    types: [opened, synchronize, edited, reopened]
+  push:
+  workflow_dispatch:
+jobs:
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        lambdapi-version: [master]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out lib
+        uses: actions/checkout@v2
+      - name: Install ocaml and opam
+        uses: ocaml/setup-ocaml@v2
+      - name: Install lambdapi dependencies
+        run: opam install dune bindlib timed sedlex menhir pratter yojson cmdliner why3
+      - name: Check out lambdapi ${{ matrix.lambdapi-version }}
+        run: git clone --depth 1 --branch ${{ matrix.lambdapi-version }} https://github.com/Deducteam/lambdapi.git
+      - name: Install lambdapi
+        run: |
+          cd lambdapi
+          eval $(opam env)
+          make install
+      - name: Check lib
+        run: |
+          eval $(opam env)
+          make