ci: add linter check to CI

.github/workflows/lint.yml

+name: Linter
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches: '*'
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install node
+        uses: actions/setup-node@v1
+        with:
+          node-version: 16
+      - name: Cache
+        uses: actions/cache@v2
+        id: cache
+        with:
+          path: '**/node_modules'
+          key: yarn-v1-${{ hashFiles('**/yarn.lock') }}
+      - name: Install
+        run: yarn --immutable
+        if: steps.cache.outputs.cache-hit != 'true'
+      - name: Lint
+        run: yarn lint

packages/loot-core/.eslintignore

+**/node_modules/*
+**/lib-dist/*
+**/proto/*

packages/loot-core/package.json

@@ -9,7 +9,7 @@
     "build:api": "cross-env NODE_ENV=development webpack --config ./webpack/webpack.api.config.js",
     "build:browser": "NODE_ENV=production ./bin/build-browser",
     "watch:browser": "NODE_ENV=development ./bin/build-browser",
-    "lint": "eslint --ignore-pattern '**/node_modules/*' --ignore-pattern '**/lib-dist/*' --ignore-pattern '**/proto/*' src"
+    "lint": "eslint src"
   },
   "author": "",
   "license": "ISC",