Site: Add description field to blog posts for RSS feed

[kevinjqliu]

Add explicit description fields to blog post to improve RSS feed quality.

The mkdocs-rss-plugin was rendering HTML comments (including the ASF license header) in the RSS feed description. By adding an explicit description field to each blog post's front matter, the plugin uses that instead of parsing the page content.

Before

After

[kevinjqliu]

@manuzhang i saw your upstream fix (Guts/mkdocs-rss-plugin#421)
claude suggested this as a workaround. ptal

[manuzhang]

@kevinjqliu I don't see an issue currently. What will be it like in a RSS reader after this change?

[kevinjqliu]

@manuzhang I think most rss readers strip out the html comment before displaying the content; i noticed the same
thing in the slack integration.

The only difference here is the raw html string. Right now, in https://iceberg.apache.org/rss.xml, the <description> field contains the html comment.

Maybe we should just let the description to be auto-generated (w/ the html comment), looks like most readers will display it properly.; and we dont expect humans to read https://iceberg.apache.org/rss.xml directly

[kevinjqliu]

Closing since readers display the description correctly. Thanks Manu!