Add mouse_clicked usage example#722

RUNQILIU-123 wants to merge 1 commit intothoth-tech:usage-examplesthoth-tech/splashkit.io-starlight:usage-examplesfrom

RUNQILIU-123:input-mouse-clicked-exampleRUNQILIU-123/splashkit.io-starlight:input-mouse-clicked-exampleCopy head branch name to clipboard