Add CI script

.github/workflows/ci.yaml

@@ -0,0 +1,18 @@
+name: CI
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: '12'
+      - name: Install dependencies
+        run: npm ci
+      - name: Run tests
+        run: npm test

README.md

@@ -1,4 +1,6 @@
 # tree-sitter-latex
 
+[![CI](https://github.com/latex-lsp/tree-sitter-latex/workflows/CI/badge.svg)](https://github.com/latex-lsp/tree-sitter-latex/actions)
+
 LaTeX grammar for [tree-sitter](https://github.com/tree-sitter/tree-sitter).
 This grammar finds use in the [TexLab](https://github.com/latex-lsp/texlab) language server.