Improve text chunk component

[adrg]

• Add Wrap method for TextChunk
• Add Fit method for TextChunk
• Refactor the paragraph component to use the newly added Wrap method
• Add TextChunk test file

Addresses #178

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This change is 

[codecov]

Codecov Report

Merging #181 into development will increase coverage by 5.94%.
The diff coverage is 90.12%.

@@               Coverage Diff               @@
##           development     #181      +/-   ##
===============================================
+ Coverage        57.54%   63.49%   +5.94%     
===============================================
  Files              189      189              
  Lines            34434    34460      +26     
===============================================
+ Hits             19815    21880    +2065     
+ Misses           12072    12070       -2     
+ Partials          2547      510    -2037

Impacted Files	Coverage Δ
creator/styled_paragraph.go	91.11% <83.33%> (+3.61%)	⬆️
creator/paragraph.go	88.73% <90%> (+5.72%)	⬆️
creator/text_chunk.go	90.19% <90.76%> (+4.83%)	⬆️
creator/division.go	89.13% <0%> (+1.08%)	⬆️
model/sighandler/sighandler_rsa_sha1.go	5.68% <0%> (+1.13%)	⬆️
model/outline.go	86.74% <0%> (+1.2%)	⬆️
creator/invoice.go	90.07% <0%> (+1.21%)	⬆️
annotator/form_field.go	14.78% <0%> (+1.4%)	⬆️
creator/toc_line.go	75.39% <0%> (+1.58%)	⬆️
internal/transform/matrix.go	61.66% <0%> (+1.66%)	⬆️
... and 125 more

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[gunnsth]

Great. Wondering whether we need to account for line height/cap height?

[gunnsth]

@adrg Can you add a note regarding the line height to the comment for Fit function. Probably the only one that needs it?

[adrg]

Sure, a note sounds like a good idea. Yes, the Wrap method does not need the line height.

[gunnsth]

LGTM