[Mobile API] Filter bookmarked games

[julien4215]

A filter to get only bookmarked games is needed in the endpoint https://lichess.org/api#tag/Games/operation/apiGamesUser.

This is for mobile pull request #1302

[ornicar]

https://lichess.org/api#tag/Games/operation/apiExportBookmarks

[julien4215]

Would it be possible to add it to then endpoint https://lichess.org/api#tag/Games/operation/apiGamesUser instead of creating a new one ?

The mobile app already implemented the pagination for this endpoint and it would also allow to combine multiple filters like only blitz and bookmarked games for example.