build(deps): update Astro to v2.1.3 and enable type checking in dev

Bump Astro from v2.0.8 to v2.1.3. Enable TypeScript type checking during development.

package.json

@@ -3,7 +3,7 @@
   "version": "2.1.0",
   "private": false,
   "scripts": {
-    "dev": "astro dev",
+    "dev": "astro check --watch & astro dev",
     "start": "astro dev",
     "build": "astro build && jampack ./dist",
     "preview": "astro preview",
@@ -18,7 +18,7 @@
   "dependencies": {
     "@astrojs/rss": "^2.1.0",
     "@resvg/resvg-js": "^2.4.1",
-    "astro": "^2.0.8",
+    "astro": "^2.1.3",
     "fuse.js": "^6.6.2",
     "github-slugger": "^2.0.0",
     "remark-collapse": "^0.1.2",