chore: add github action for test

.github/workflows/test.yaml

@@ -0,0 +1,43 @@
+name: Test
+on:
+  push:
+    paths:
+      - "lua/**"
+  pull_request:
+    paths:
+      - "lua/**"
+
+jobs:
+  run_tests:
+    name: unit tests
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu22.04]
+        rev:
+          [
+            nightly/nvim-linux64.tar.gz,
+            v0.8.2/nvim-linux64.tar.gz,
+            v0.7.2/nvim-linux64.tar.gz,
+          ]
+    steps:
+      - uses: actions/checkout@v3
+      - run: date +%F > todays-date
+      - name: Restore cache for today's nightly.
+        uses: actions/cache@v3
+        with:
+          path: _neovim
+          key: ${{ runner.os }}-${{ matrix.rev }}-${{ hashFiles('todays-date') }}
+      - name: Prepare
+        run: |
+          test -d _neovim || {
+            mkdir -p _neovim
+            curl -sL "https://github.com/neovim/neovim/releases/download/${{ matrix.rev }}" | tar xzf - --strip-components=1 -C "${PWD}/_neovim"
+          }
+      - name: Run tests
+        run: |
+          export PATH="${PWD}/_neovim/bin:${PATH}"
+          export VIM="${PWD}/_neovim/share/nvim/runtime"
+          nvim --version
+          make test