Serve image assets from Khoj domain, not directly from S3 bucket (#734)

- Serve generated images from Khoj domain instead of directly from AWS S3
- Rename assets URL from Khoj S3 bucket to assets.khoj.dev

documentation/docs/data-sources/share_your_data.md

@@ -13,4 +13,4 @@ There are several ways you can get started with sharing your data with the Khoj
 - Setup the sync options for either [Obsidian](/clients/obsidian) or [Emacs](/clients/emacs) to automatically sync your documents with Khoj. This is best if you are already using these tools and want to leverage Khoj's AI capabilities.
 - Configure your [Notion](/data-sources/notion_integration) or [Github](/data-sources/github_integration) to sync with Khoj. By providing your credentials, you can keep the data synced in the background.
 
-![demo of dragging and dropping a file](https://khoj-web-bucket.s3.amazonaws.com/drag_drop_file.gif)
+![demo of dragging and dropping a file](https://assets.khoj.dev/drag_drop_file.gif)

documentation/docusaurus.config.js

@@ -80,7 +80,7 @@ const config = {
         {name: 'og:type', content: 'website'},
         {name: 'og:site_name', content: 'Khoj Documentation'},
         {name: 'og:description', content: 'Quickly get started with using or self-hosting Khoj'},
-        {name: 'og:image', content: 'https://khoj-web-bucket.s3.amazonaws.com/link_preview_docs.png'},
+        {name: 'og:image', content: 'https://assets.khoj.dev/link_preview_docs.png'},
         {name: 'og:url', content: 'https://docs.khoj.dev'},
         {name: 'keywords', content: 'khoj, khoj ai, chatgpt, open ai, open source, productivity'}
       ],