tune linting so it doesn't produce errors anymore and enable in CI

.eslintignore

@@ -0,0 +1 @@
+src/matrix/storage/memory

.eslintrc.js

@@ -10,6 +10,8 @@ module.exports = {
     },
     "rules": {
         "no-console": "off",
-        "no-empty": "off"
+        "no-empty": "off",
+        "no-prototype-builtins": "off",
+        "no-unused-vars": "warn",
     }
 };

.github/workflows/checks.yml

@@ -1,7 +1,7 @@
 # This workflow will do a clean install of node dependencies, build the source code and run tests across different versions of node
 # For more information see: https://help.github.com/actions/language-and-framework-guides/using-nodejs-with-github-actions
 
-name: Unit tests
+name: Code checks
 
 on:
   push:
@@ -20,9 +20,12 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Run unit tests
+    - name: Install
       uses: actions/setup-node@v2
       with:
         node-version: ${{ matrix.node-version }}
     - run: npm install --also=dev
+    - name: Unit tests
     - run: npm test
+    - name: Lint
+    - run: npm run lint-ci

.gitignore

@@ -7,3 +7,4 @@ bundle.js
 target
 lib
 *.tar.gz
+.eslintcache

package.json

@@ -7,7 +7,8 @@
     "doc": "doc"
   },
   "scripts": {
-    "lint": "eslint src/",
+    "lint": "eslint --cache src/",
+    "lint-ci": "eslint src/",
     "test": "impunity --entry-point src/main.js --force-esm-dirs lib/ src/",
     "start": "node scripts/serve-local.js",
     "build": "node --experimental-modules scripts/build.mjs",