feat: relative time timer for segments

[TheWarior73]

Solves #1

Added :

• Color-coded relative timer to Personal-Best for a given segment

• Toggle button in BlendSplit > Overlay > Visible Information > Show Relative Time

Note :

• Resizing the overlay does work accordingly

• Time value for a given segment are now TEXT colored and MUTED when a run is ongoing and the segment has not yet been completed.

Thinking of possibly adding color back to the time value when the Relative time information is hidden

[TheWarior73]

I am now noticing that I did not include new unit tests...
I can try to add some, but I have never used unit tests before and am quite a bit rusty in python so I can't really promise that the results will be adequate.

Side note, any feedback is appreciated (on the feature, behaviour, code implementation) :3
This is a first for me to contribute to an open source project and it is in my best interest to make it as best as I can !