Add tests, lint, formatting, and ci

.eslintignore

@@ -0,0 +1,6 @@
+dist
+coverage
+node_modules
+__tests__/__fixtures__/file.js
+!.prettierrc.cjs
+!.eslintrc.cjs

.eslintrc.cjs

@@ -0,0 +1,18 @@
+module.exports = {
+  env: {
+    es6: true,
+    node: true,
+    jest: true
+  },
+  extends: [
+    'eslint:recommended',
+    'plugin:jest/recommended',
+    'plugin:prettier/recommended'
+  ],
+  parser: '@babel/eslint-parser',
+  parserOptions: {
+    ecmaVersion: '2020',
+    sourceType: 'module'
+  },
+  plugins: ['jest', 'prettier']
+}

.github/workflows/ci.yml

@@ -0,0 +1,41 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/[email protected]
+      - name: Setup Node
+        uses: actions/setup-node@v1
+        with:
+          node-version: '16.5.0'
+      - name: Cache
+        uses: actions/[email protected]
+        with:
+          path: ~/.npm
+          key: ${{ runner.os }}-node-${{ hashFiles('package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+      - name: Install Dependencies
+        run: npm ci
+      - name: Save error log
+        uses: actions/upload-artifact@v2
+        if: ${{ failure() }}
+        with:
+          name: npm-debug-log-${{ hashFiles('package-lock.json') }}
+          path: npm-debug.log
+      - name: Test
+        run: npm test
+      - name: Lint
+        run: npm run lint
+      - name: Pack
+        run: npm pack

.gitignore

@@ -1,3 +1,4 @@
 *.tgz
 dist
 node_modules
+coverage

.prettierrc.cjs

@@ -0,0 +1,10 @@
+module.exports = {
+  printWidth: 90,
+  tabWidth: 2,
+  useTabs: false,
+  semi: false,
+  singleQuote: true,
+  trailingComma: 'none',
+  bracketSpacing: true,
+  arrowParens: 'avoid'
+}