chore(changelog): make the scopes lowercase in the changelog

[orhun]

Before:

### Documentation

- [0c68ebe](https://github.com/ratatui-org/ratatui/commit/0c68ebed4f63a595811006e0af221b11a83780cf)
  *(Block)* Add documentation to Block ([#469](https://github.com/ratatui-org/ratatui/issues/469))

After:

### Documentation

- [0c68ebe](https://github.com/ratatui-org/ratatui/commit/0c68ebed4f63a595811006e0af221b11a83780cf)
  *(block)* Add documentation to Block ([#469](https://github.com/ratatui-org/ratatui/issues/469))

[codecov]

Codecov Report

Merging #479 (3a0798d) into main (0c68ebe) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #479   +/-   ##
=======================================
  Coverage   90.06%   90.06%           
=======================================
  Files          40       40           
  Lines       11166    11166           
=======================================
  Hits        10057    10057           
  Misses       1109     1109           

[joshka]

I hate that there's no way to make the release notes in the releases tab render this without the newline without removing it entirely (leading to a long line in the markdown) e.g.:

- [0c68ebe](https://github.com/ratatui-org/ratatui/commit/0c68ebed4f63a595811006e0af221b11a83780cf) *(block)* Add documentation to Block ([#469](https://github.com/ratatui-org/ratatui/issues/469))

• 0c68ebe (block) Add documentation to Block (#469)