- Linting (ESLint compat): Add eslint-plugin-compat to get browser support

warnings
- Docs (README): Indicate minimal polyfills needed for older browsers
    (IE <= 11, IE Mobile, Opera Mini, Blackberry Browser <= 10,
    Android Browser 4.4.3-4.4.4)
- npm: Update devDeps

.eslintrc

@@ -1,13 +1,19 @@
 {
-  "extends": ["standard", "plugin:qunit/recommended", "plugin:testcafe/recommended"],
+  "extends": [
+    "standard", "plugin:compat/recommended",
+    "plugin:qunit/recommended", "plugin:testcafe/recommended"
+  ],
   "parserOptions": {
     "sourceType": "module"
   },
-  "plugins": ["qunit", "testcafe"],
+  "plugins": ["compat", "qunit", "testcafe"],
   "env": {
     "node": false,
     "browser": true
   },
+  "settings": {
+    "polyfills": ["url", "promises", "fetch", "queryselector"]
+  },
   "rules": {
     "semi": [2, "always"],
     "indent": ["error", 2, {"outerIIFEBody": 0}],