chore: setup linting

app/eslint.config.mjs

@@ -0,0 +1,37 @@
+import { includeIgnoreFile } from '@eslint/compat';
+import js from '@eslint/js';
+import svelte from 'eslint-plugin-svelte';
+import { defineConfig } from 'eslint/config';
+import globals from 'globals';
+import path from 'node:path';
+import ts from 'typescript-eslint';
+import svelteConfig from './svelte.config.js';
+
+const gitignorePath = path.resolve(import.meta.dirname, '.gitignore');
+
+export default defineConfig(
+  includeIgnoreFile(gitignorePath),
+  js.configs.recommended,
+  ...ts.configs.recommended,
+  ...svelte.configs.recommended,
+  {
+    languageOptions: { globals: { ...globals.browser, ...globals.node } },
+    rules: {
+      // typescript-eslint strongly recommend that you do not use the no-undef lint rule on TypeScript projects.
+      // see: https://typescript-eslint.io/troubleshooting/faqs/eslint/#i-get-errors-from-the-no-undef-rule-about-global-variables-not-being-defined-even-though-there-are-no-typescript-errors
+      'no-undef': 'off'
+    }
+  },
+  {
+    files: ['**/*.svelte', '**/*.svelte.ts', '**/*.svelte.js'],
+    languageOptions: {
+      parserOptions: {
+        projectService: true,
+        extraFileExtensions: ['.svelte'],
+        parser: ts.parser,
+        tsconfigRootDir: import.meta.dirname,
+        svelteConfig
+      }
+    }
+  }
+);