Character spacing

[adrg]

Add TextStyle character spacing field.
Integrate character spacing into the StyledParagraph component.

Resolves #119

[codecov]

Codecov Report

Merging #338 into v3 will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##               v3     #338      +/-   ##
==========================================
+ Coverage   58.19%   58.22%   +0.03%     
==========================================
  Files         145      145              
  Lines       25217    25231      +14     
==========================================
+ Hits        14674    14692      +18     
+ Misses      10176    10170       -6     
- Partials      367      369       +2

Impacted Files	Coverage Δ
pdf/creator/text_style.go	100% <ø> (ø)	⬆️
pdf/creator/styled_paragraph.go	92.27% <100%> (-0.23%)	⬇️
pdf/model/image.go	57.82% <0%> (-1.37%)	⬇️
pdf/model/optimize/image.go	78.04% <0%> (-1.22%)	⬇️
pdf/creator/image.go	83.33% <0%> (-0.65%)	⬇️
pdf/core/primitives.go	77.65% <0%> (-0.64%)	⬇️
pdf/creator/invoice.go	89.58% <0%> (-0.49%)	⬇️
pdf/model/functions.go	49.11% <0%> (-0.45%)	⬇️
pdf/extractor/text.go	68.06% <0%> (-0.44%)	⬇️
... and 19 more

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[gunnsth-review]

Reviewed 3 of 3 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved