ci: add typescript capability and a11y linting

eslint.config.mjs

@@ -1,7 +1,8 @@
 import js from "@eslint/js";
-import { defineConfig } from "eslint/config";
 import eslintPluginAstro from "eslint-plugin-astro";
 import eslintPluginPrettierRecommended from "eslint-plugin-prettier/recommended";
+import { defineConfig } from "eslint/config";
+import jsxA11y from "eslint-plugin-jsx-a11y";
 
 export default defineConfig([
   {
@@ -9,6 +10,12 @@ export default defineConfig([
     plugins: { js },
     extends: ["js/recommended"],
   },
+  {
+    files: ["**/*.{astro,html}"],
+    plugins: {
+      "jsx-a11y": jsxA11y,
+    },
+  },
   ...eslintPluginAstro.configs.recommended,
   eslintPluginPrettierRecommended,
 ]);