Games library: sort options and jump-to-letter navigation

Follow-up to the new games database (include/raylib-libretro-games.h).

The Games list is currently sorted by title only. Add sort options and fast navigation for large libraries.

Proposal

• Sort options (combobox on the Games page): Title (A-Z / Z-A), System, Recently added, Recently played (depends on #(favorites/recently-played)), File size. Easy with SQL ORDER BY, or by re-sorting the in-memory filtered index.
• Jump-to-letter: pressing a letter (or a shoulder-button alphabet strip) jumps the list selection to the first title starting with that letter — important for thousands of entries in nk_console_list_view.
• Optional: a small header showing the current count / position.

Notes

• Builds on the existing LibretroGamesRebuildFiltered + nk_console_list_view in include/raylib-libretro-menu.h.

Start by reading include/raylib-libretro-menu.h, especially LibretroGamesRebuildFiltered and the nk_console_list_view usage, then inspect include/raylib-libretro-games.h for the games data. Confirm how favorites and recently played are represented before choosing the sort source. Done means the Games page offers the requested ordering choices and lets users jump to titles by initial letter in large libraries.