doc(ui): Improve documentation of RoomListLoadingState

[Hywan]

This patch adds intra-links and clarifies a sentence about the room type.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.60%. Comparing base (4ae82dd) to head (594cf14).
⚠️ Report is 15 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5880   +/-   ##
=======================================
  Coverage   88.60%   88.60%           
=======================================
  Files         363      363           
  Lines      102926   102926           
  Branches   102926   102926           
=======================================
  Hits        91194    91194           
- Misses       7490     7492    +2     
+ Partials     4242     4240    -2     

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[codspeed-hq]

CodSpeed Performance Report

Merging #5880 will not alter performance

_{Comparing Hywan:doc-ui-room-list-loading-state (594cf14) with main (b1eaa5e)}

Summary

✅ 50 untouched