dep: update dependencies

更新了 @astrojs/rss @astrojs/sitemap astro giscus rehype-mathjax remark-join-cjk-lines sanitize-html
remark-math 暂未更新：remarkjs/remark-math#89 (comment)

fix: 将 feed.xml.js 中 get 重命名为 GET

package.json

@@ -13,14 +13,14 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@astrojs/rss": "^2.4.3",
-    "@astrojs/sitemap": "^1.3.2",
-    "astro": "^2.5.6",
-    "giscus": "^1.2.8",
+    "@astrojs/rss": "^3.0.0",
+    "@astrojs/sitemap": "^3.0.3",
+    "astro": "^3.5.3",
+    "giscus": "^1.3.0",
     "lunar-calendar": "^0.1.4",
-    "rehype-mathjax": "^4.0.2",
-    "remark-join-cjk-lines": "^1.0.9",
+    "rehype-mathjax": "^5.0.0",
+    "remark-join-cjk-lines": "^1.0.11",
     "remark-math": "^5.1.1",
-    "sanitize-html": "^2.10.0"
+    "sanitize-html": "^2.11.0"
   }
 }