Style for Load More rankings button

[datlechin]

Fixes #0000

Changes proposed in this pull request: Style for Load More rankings button

Screenshot Before

After

Confirmed

• [ ] Frontend changes: tested on a local Flarum installation.
• [ ] Backend changes: tests are green (run composer test).

Required changes:

• [ ] Related Flarum core extension PR's: (Omit this section if irrelevant)