test : added unit tests for lib/rss module - #7

Summary of What Has Been Done

Created lib/rss.test.ts with comprehensive unit tests covering:

• Parses dev.to feed and returns up to 3 articles with correct fields
• Constructs the correct hashnode feed URL for standard usernames
• Strips .hashnode.dev suffix before constructing the URL
• Uses custom domain URL when username contains a dot and is not a standard username
• Uses direct URL when username starts with https://
• Returns an empty array on network errors (no throw)
• Defaults title to 'Untitled' when missing
• Defaults link to empty string when missing
• Defaults pubDate to empty string when missing
• Formats pubDate using toLocaleDateString

Mocked the rss-parser module to provide controlled fixture data without network calls.

Changes Made

• New file: lib/rss.test.ts

Impact it Made

Adds first unit test coverage for the RSS feed module, ensuring robust feed parsing for both dev.to and hashnode platforms with proper error handling.

Closes #8422.

Note: please assign this PR to the tmdeveloper007 account.