refactor!: convert to Polymer 3

vaadin/vaadin-element-mixin#41

Author: web-padawan

packages/vaadin-element-mixin/.eslintrc.json

@@ -1,21 +1,15 @@
 {
-  "extends": "vaadin",
+  "extends": [
+    "eslint:recommended",
+    "plugin:prettier/recommended"
+  ],
+  "plugins": ["prettier"],
   "env": {
     "browser": true,
-    "node": true,
     "es6": true
   },
-  "plugins": [
-    "html"
-  ],
-  "globals": {
-    "Polymer": false,
-    "Vaadin": false
-  },
-  "rules": {
-    "arrow-spacing": "error"
-  },
   "parserOptions": {
-    "ecmaVersion": 2017
+    "sourceType": "module",
+    "ecmaVersion": 2020
   }
 }

packages/vaadin-element-mixin/.github/workflows/sauce.yml

@@ -0,0 +1,28 @@
+name: sauce
+
+on:
+  push:
+    branches:
+      - '**'
+    tags-ignore:
+      - '*.*'
+
+jobs:
+  unit-tests:
+    runs-on: ubuntu-latest
+    if: "! contains(toJSON(github.event.commits.*.message), '[skip ci]')"
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+      with:
+        node-version: 12
+
+    - name: Install dependencies
+      run: npm install
+
+    - name: SauceLabs tests
+      env:
+        SAUCE_USERNAME: ${{ secrets.SAUCE_USERNAME }}
+        SAUCE_ACCESS_KEY: ${{ secrets.SAUCE_ACCESS_KEY }}
+      run: npm run test:sauce

packages/vaadin-element-mixin/.github/workflows/tests.yml

@@ -0,0 +1,22 @@
+name: tests
+
+on: [pull_request]
+
+jobs:
+  unit-tests:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-node@v1
+      with:
+        node-version: 12
+
+    - name: Install dependencies
+      run: npm install
+
+    - name: Lint JavaScript
+      run: npm run lint
+
+    - name: Unit tests
+      run: npm test

packages/vaadin-element-mixin/.gitignore

@@ -1,2 +1,3 @@
 bower_components
 node_modules
+coverage

packages/vaadin-element-mixin/.npmignore

@@ -0,0 +1,6 @@
+{
+  "singleQuote": true,
+  "printWidth": 120,
+  "trailingComma": "none",
+  "htmlWhitespaceSensitivity": "strict"
+}