chore(lint): add eslint and prettier with ionic configs and CI workflow

.github/CONTRIBUTING.md

@@ -53,6 +53,8 @@ Talk to us before creating a PR that refactors the code or directory structure o
 
 Make sure to follow the existing code style as much as possible.
 
+Code is linted with ESLint and formatted with Prettier, and pull requests must pass `npm run lint`. Run `npm run lint:fix` to fix what can be fixed automatically.
+
 * No underscores prefixing JS functions.
 * Use flat Sass:
   * **Don't** use [BEM conventions](https://css-tricks.com/bem-101/)

.github/workflows/CI.yml

@@ -0,0 +1,49 @@
+# GitHub Actions docs
+# https://help.github.com/en/articles/about-github-actions
+# https://help.github.com/en/articles/workflow-syntax-for-github-actions
+
+name: Install Dependencies, Lint and Build
+
+on: [pull_request]
+
+jobs:
+  lint:
+    name: Lint
+    # Lint once on Linux. Windows runners check out with CRLF line endings,
+    # which Prettier would report as formatting changes.
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+    - name: Use Node.js 24
+      uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+      with:
+        node-version: 24
+    - name: Install Dependencies
+      run: npm ci
+    - name: Lint
+      run: npm run lint
+
+  test:
+    name: Test on node ${{ matrix.node_version }} and ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        # When node version is updated, update the version in the GitHub repository settings (admin access required):
+        # Branches -> Edit `main` -> Protect matching branches ->
+        # Require status checks to pass before merging ->
+        # Search for the new version -> Add them to the list ->
+        # Remove the old version from the list -> Save changes
+        node_version: [24]
+        os: [windows-latest, macOS-latest]
+
+    steps:
+    - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+    - name: Use Node.js ${{ matrix.node_version }}
+      uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+      with:
+        node-version: ${{ matrix.node_version }}
+    - name: Install Dependencies
+      run: npm ci
+    - name: Build
+      run: npm run build

.prettierignore

@@ -0,0 +1,5 @@
+# Prettier only reads the root .gitignore, not the ones inside the native
+# projects, so ignore them here to skip Capacitor's copied web build and
+# Gradle's build output.
+android/
+ios/

.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+  "recommendations": [
+    "dbaeumer.vscode-eslint",
+    "esbenp.prettier-vscode",
+    "Webnative.webnative"
+  ]
+}

eslint.config.mjs

@@ -0,0 +1,42 @@
+import ionic from '@ionic/eslint-config/recommended.js';
+import { defineConfig } from 'eslint/config';
+import reactHooks from 'eslint-plugin-react-hooks';
+import reactRefresh from 'eslint-plugin-react-refresh';
+import globals from 'globals';
+
+export default defineConfig([
+  { ignores: ['dist/**', 'android/**', 'ios/**'] },
+  ionic,
+  {
+    files: ['**/*.{ts,tsx}'],
+    extends: [reactHooks.configs.flat.recommended, reactRefresh.configs.vite],
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.node,
+      },
+    },
+    rules: {
+      // Ionic's base level; `recommended` makes it an error, which is meant for libraries.
+      '@typescript-eslint/explicit-module-boundary-types': 'warn',
+      // Every page exports both the component and a `connect()`-wrapped default,
+      // which fast refresh can't follow. Revisit if the custom connect HOC in
+      // data/connect.tsx is replaced with hooks.
+      'react-refresh/only-export-components': 'off',
+      // `connect()` and several page props use `{}` as an empty-props generic.
+      '@typescript-eslint/no-empty-object-type': 'off',
+      // The demo uses `cond && fn()` and ternaries for side effects throughout.
+      '@typescript-eslint/no-unused-expressions': 'off',
+    },
+  },
+  {
+    // The snapshot test predates the current tooling and has no runner; it is
+    // still typechecked by `tsc`, so keep it linted with jest globals defined.
+    files: ['**/*.test.{ts,tsx}'],
+    languageOptions: {
+      globals: {
+        ...globals.jest,
+      },
+    },
+  },
+]);