Scale endgame default depth

[ddugovic]

Possibly this may involve a larger conversation with Lichess about how analysis is done, but in endgames (or shallow positions in general which search a low node count per depth) it may be desirable to search deeper than 25 plies without resorting to go infinite.

[NiclasSchwalbe]

Should this not be already be possible?

[niklasf]

Here's how this is solved for the in-browser engine: https://github.com/lichess-org/lila/blob/55da1b90a22c42604b5f8ac3288f5b84c3927c66/ui/ceval/src/protocol.ts#L146-L152

The focus of the example provider here is to demonstrate the API, but of course it could do something similar. Would accept a PR.