[UX] VirtualKeyPopup: close on hold release (#4891)
[UX] VirtualKeyPopup: close on hold release (#4891)

As suggested by @poire-z.

NiLuJe/koreader,mihailim/koreader,koreader/koreader,Frenzie/koreader,koreader/koreader,houqp/koreader,NiLuJe/koreader,Markismus/koreader,Hzj-jie/koreader,mwoz123/koreader,poire-z/koreader,poire-z/koreader,Frenzie/koreader,pazos/koreader