feat: add ESLint and update linting errors (#26)

* Install ESLint and Astro ESLint plugin

* Configure 2 plugins

* Improve ignore files

* Add lint script

* Install astro-eslint-parser

* Add parser and fix linting errors

.eslintrc.js

@@ -0,0 +1,23 @@
+module.exports = {
+  env: {
+    node: true,
+    es2022: true,
+    browser: true,
+  },
+  extends: ["eslint:recommended", "plugin:astro/recommended"],
+  parserOptions: {
+    ecmaVersion: "latest",
+    sourceType: "module",
+  },
+  overrides: [
+    {
+      files: ["*.astro"],
+      parser: "astro-eslint-parser",
+      parserOptions: {
+        parser: "@typescript-eslint/parser",
+        extraFileExtensions: [".astro"],
+      },
+      rules: {},
+    },
+  ],
+};