style: add eslint and prettier

eslint.config.mjs

@@ -0,0 +1,55 @@
+// @ts-check
+
+import eslint from "@eslint/js";
+import tseslint from "typescript-eslint";
+import eslintConfigPrettier from "eslint-config-prettier/flat";
+import { globalIgnores } from "eslint/config";
+import svelte from "eslint-plugin-svelte";
+import globals from "globals";
+import svelteConfig from "./svelte.config.js";
+
+export default tseslint.config(
+	eslint.configs.recommended,
+	tseslint.configs.recommended,
+	tseslint.configs.stylistic,
+	...svelte.configs.recommended,
+	eslintConfigPrettier,
+	{
+		rules: {
+			"@typescript-eslint/no-unused-vars": [
+				"error",
+				{
+					argsIgnorePattern: "^_",
+					varsIgnorePattern: "^_",
+					caughtErrorsIgnorePattern: "^_",
+				},
+			],
+		},
+	},
+	[globalIgnores(["./android", "./dist"])],
+	{
+		languageOptions: {
+			globals: {
+				...globals.browser,
+			},
+		},
+	},
+	{
+		files: ["**/*.svelte", "**/*.svelte.ts", "**/*.svelte.js"],
+		languageOptions: {
+			parserOptions: {
+				projectService: true,
+				extraFileExtensions: [".svelte"], // Add support for additional file extensions, such as .svelte
+				parser: tseslint.parser,
+				// We recommend importing and specifying svelte.config.js.
+				// By doing so, some rules in eslint-plugin-svelte will automatically read the configuration and adjust their behavior accordingly.
+				// While certain Svelte settings may be statically loaded from svelte.config.js even if you don’t specify it,
+				// explicitly specifying it ensures better compatibility and functionality.
+				svelteConfig,
+			},
+		},
+		rules: {
+			"no-undef": "off",
+		},
+	},
+);