Add relativeCoords average to PointerTracker

[m-bert]

Description

This PR adds missing relativeCoords average in PointerTracker.

Test plan

Add console.log(this.tracker.getRelativeCoordsAverage()); in onPointerMove callback inside PanGestureHandler and check that logs contain average position.

[m-bert]

Here I see two options:

• We can leave 2 methods, one for absolute and one for relative coords
• We can merge them into one method

The second option could look like this:

public getAverageCoords(relative = false) {
  // calculate average
}

It can be done in different ways (default value, optional argument, required argument), but you get the point. Let me know what do you think. cc @j-piasecki, @latekvo

[latekvo]

I think it would be better to follow the convention, right below there are getAbsoluteCoordsSum() and getRelativeCoordsSum() functions.

And while this creates a bit more duplicate code, I also think it's more readable than having a single function with an optional boolean argument.
Perhaps the second option would work fine with a positional argument or an enum, since these are more verbose, but i think it would be simpler to just go with the first option.

But of course it's best to wait for j-piasecki's opinion 👍

[j-piasecki]

Yeah, I think keeping them separate makes sense. They are not that long and, unless I'm missing something, the only part that would apply to both cases would be calculating the average so we wouldn't get that much from merging the two.

[j-piasecki]

🪨