Fix MrCongRipper to use new URL misskon.com (Fixes #2127)

[metaprime]

Category

This change is exactly one of the following (please change [ ] to [x]) to indicate which:

• a bug fix (Fix MrCongRipper not working - URL changed #2127)
• a new Ripper
• a refactoring
• a style change/fix
• a new feature

Description

This ripper was previously for mrcong.com, which now redirects to
misskon.com. Some resources still refer to mrcong.com
but all the top level URLs are now misskon.com

Testing

Required verification:

• I've verified that there are no regressions in gradlew test (there are no new failures or errors).
• I've verified that this change works as intended.
  • Downloads all relevant content.
  • Downloads content from multiple pages (as necessary or appropriate).
  • Saves content at reasonable file names (e.g. page titles or content IDs) to help easily browse downloaded content.
• I've verified that this change did not break existing functionality (especially in the Ripper I modified).

Optional but recommended:

• I've added a unit test to cover my change.

[Copilot]

Pull Request Overview

This PR fixes MrCongRipper to use the new URL domain misskon.com (Fixes #2127) by updating domain references and related URL processing.

• Updated host and domain references from mrcong.com to misskon.com in both main and test files.
• Modified regex patterns and exception messages to match the new URL format.
• Changed image source attribute extraction from "src" to "data-src" to support lazy-loaded images.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/test/java/com/rarchives/ripme/tst/ripper/rippers/MrCongRipperTest.java	Updated tests to reference misskon.com URLs.
src/main/java/com/rarchives/ripme/ripper/rippers/MrCongRipper.java	Adjusted domain, regex patterns, and image attribute extraction for new URL behaviors.