Allow cursor grab on web using pointer lock API

[LioQing]

Is your feature request related to a problem? Please describe.
Currently, sending ViewportCommand::CursorGrab to viewport command on web does nothing. Console outputs state that it is not supported on the web.

Describe the solution you'd like
The command should be able to lock the cursor by using the pointer lock API.

Describe alternatives you've considered
Can't find any alternatives on the internet but there was #1605 which seems to be outdated and unrelated.