feat: add RSS feed beautification option

Introduces a new RSS_BEAUTIFY configuration flag to enable RSS feed styling
- Adds XSL styling support for RSS feeds when enabled
- Updates documentation in both English and Chinese
- Modifies RSS generation to support the new styling option

Migration from rss to getRssString for enhanced customization

.env.example

@@ -23,4 +23,5 @@ GOOGLE_SEARCH_SITE=""
 TAGS=""
 COMMENTS=""
 LINKS=""
-NAVS=""
+NAVS=""
+RSS_BEAUTIFY=false

README.md

@@ -133,6 +133,9 @@ LINKS=Title1,URL1;Title2,URL3;Title3,URL3;
 
 ## Sidebar Navigation Item, Separate using commas and semicolons
 NAVS=Title1,URL1;Title2,URL3;Title3,URL3;
+
+## Enable RSS beautify
+RSS_BEAUTIFY=true
 ```
 
 ## 🙋🏻 FAQs

README.zh-cn.md

@@ -131,6 +131,9 @@ LINKS=Title1,URL1;Title2,URL3;Title3,URL3;
 
 ## 侧边栏导航项, 使用英文逗号和分号分割
 NAVS=Title1,URL1;Title2,URL3;Title3,URL3;
+
+## 启用 RSS 美化
+RSS_BEAUTIFY=true
 ```
 
 ## 🙋🏻 常问问题

src/pages/rss.xml.js

@@ -1,6 +1,8 @@
-import rss from '@astrojs/rss'
+import { getRssString } from '@astrojs/rss'
 import sanitizeHtml from 'sanitize-html'
 import { getChannelInfo } from '../lib/telegram'
+import { getEnv } from '../lib/env'
+import style from '../assets/rss.xsl?raw'
 
 export async function GET(Astro) {
   const { SITE_URL } = Astro.locals
@@ -15,7 +17,7 @@ export async function GET(Astro) {
   url.pathname = SITE_URL
   url.search = ''
 
-  return rss({
+  let rssString = await getRssString({
     title: `${tag ? `${tag} | ` : ''}${channel.title}`,
     description: channel.description,
     site: url.origin,
@@ -39,4 +41,16 @@ export async function GET(Astro) {
       }),
     })),
   })
+
+  const enableBeautify = getEnv(import.meta.env, Astro, 'RSS_BEAUTIFY')
+  if (enableBeautify) {
+    rssString = rssString.replace(/^(<\?xml .*\?>)/i, style)
+  }
+
+  return new Response(rssString, {
+    headers: {
+      'Content-Type': 'text/xml',
+      'Cache-Control': 'public, max-age=3600',
+    },
+  })
 }