Add eslint to help maintain higher code standards (#315)

The most important part of having eslint here is the checks in
`eslint-plugin-react-hooks` which help check some of the most critical
usage patterns when it comes to writing React code.

.github/workflows/npm.yaml

@@ -7,14 +7,33 @@ on:
     branches: [main, dev]
 
 jobs:
-  build_and_test:
+  build:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
           node-version: 20
+          cache: npm
       - run: npm ci
       - run: npm run build
-      - run: npm run typecheck
+  eslint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+      - run: npm ci
+      - run: npm run eslint
+  stylelint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+      - run: npm ci
       - run: npm run stylelint

eslint.config.mjs

@@ -0,0 +1,25 @@
+import globals from 'globals';
+import pluginJs from '@eslint/js';
+import pluginReact from 'eslint-plugin-react';
+import pluginReactHooks from 'eslint-plugin-react-hooks';
+
+/** @type {import('eslint').Linter.Config[]} */
+export default [
+  { files: ['**/*.{js,mjs,cjs,jsx}'] },
+  { languageOptions: { globals: globals.browser } },
+  pluginJs.configs.recommended,
+  pluginReact.configs.flat.recommended,
+  pluginReact.configs.flat['jsx-runtime'],
+  pluginReactHooks.configs['recommended-latest'],
+  {
+    settings: {
+      react: {
+        version: 'detect',
+      },
+    },
+    rules: {
+      'react/prop-types': 'off',
+      'no-unused-vars': 'off',
+    },
+  },
+];