[Feature] Add millisecond (or frame) precision to markers

[BonerFide]

Is your feature request related to a problem? Please describe.
It's difficult to get markers to start / end at the right time when they only have second precision, sometimes the half second before is too early, and the half second after too late.

Describe the solution you'd like
Markers should be able to be created using the interface from the exact current position of the player with ms / or frame precision.

Describe alternatives you've considered
The loop plugin could also be used to set/create/be set by markers.

Additional context
The database already stores markers as floats, so the database should support this, it just needs the interface to allow that precision.
This pull request adds end time, which should also have the same interface / precision change.
#5311