chore: complete ESLint v9 configuration

eslint.config.js

@@ -1,5 +1,35 @@
-export default [
+import { defineConfig, globalIgnores } from 'eslint/config';
+import js from '@eslint/js';
+import globals from 'globals';
+
+export default defineConfig([
+  globalIgnores(['assets/*', 'node_modules/*', '_site/*']),
+  js.configs.recommended,
   {
-    files: ['_javascript/**/*.js']
+    rules: {
+      semi: ['error', 'always'],
+      quotes: ['error', 'single']
+    },
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        ...globals.node
+      }
+    }
+  },
+  {
+    files: ['_javascript/**/*.js'],
+    languageOptions: {
+      globals: {
+        ClipboardJS: 'readonly',
+        GLightbox: 'readonly',
+        Theme: 'readonly',
+        dayjs: 'readonly',
+        mermaid: 'readonly',
+        tocbot: 'readonly',
+        importScripts: 'readonly',
+        swconf: 'readonly'
+      }
+    }
   }
-];
+]);