Add support for tracking (letter-spacing)

[Socolin]

Introduces a Tracking property to TextOptions to allow uniform adjustment of spacing between characters, measured in em units.

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Description

I'm not sure:

• If the unit, if it should be in em or milliem of em or something else.
• If the name of the feature, if it should be Tracking or a more user friendly like in css LetterSpacing ?
• If this need more tests, since the rendering is in ImageSharp.Drawing I don't know if I should add some test comparing images instead of just checking values

I did some simple render test and it seems to works and give the same result as Chrome

Top: Chrome
Below: ImageSharp

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83%. Comparing base (bc2501d) to head (96e500f).
⚠️ Report is 75 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #492     +/-   ##
=======================================
- Coverage     87%     83%     -4%     
=======================================
  Files        238     272     +34     
  Lines      15457   18930   +3473     
  Branches    2187    2676    +489     
=======================================
+ Hits       13452   15837   +2385     
- Misses      1538    2422    +884     
- Partials     467     671    +204     

Flag	Coverage Δ
unittests	83% <100%> (-4%)	⬇️

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[Socolin]

The new code still have a bug.

\u0930\u094D\u0915\u093F is printing with tracking = 1

And with tracking = 0 (Correct)

Do you have an idea of what is the problem with this one ?

It's one of the unit test in this PR

[JimBobSquarePants]

The new code still have a bug.

\u0930\u094D\u0915\u093F is printing with tracking = 1

And with tracking = 0 (Correct)

Do you have an idea of what is the problem with this one ?

It's one of the unit test in this PR

I think so. We should be checking the grapheme index I think.

[Socolin]

The graphemeIndex and graphemeCodePointIndex values are [0,0,1] I'm not sure we can do much with it or if there is a problem elsewhere because I found a bug with this character too when rendering it in Vertical mode:

So maybe fixing it in vertical mode will fix for this scenario too ? I have no idea how to investigate the problem here, do you want me to open another issue for this ?

[JimBobSquarePants]

@Socolin I'll need to pull down your fork to fix the PR as the fix is quite complex.