Add Github Actions CI job that lints vimscript

.github/workflows/vint.yml

@@ -0,0 +1,16 @@
+name: Vint
+on: [push, pull_request]
+jobs:
+  vint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@master
+      - name: Set up Python
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.7
+      - name: Setup dependencies
+        run: pip install vim-vint
+      - name: Run Vimscript Linter
+        run: vint .