Added support for drawing polygons and polylines

[akohring]

This change is 

[CLAassistant]

All committers have signed the CLA.

[codecov[bot]]

Codecov Report

Merging #396 into master will decrease coverage by 4.90%. The diff coverage is 88.61%.

@@            Coverage Diff             @@
##           master     #396      +/-   ##
==========================================
- Coverage   57.34%   52.43%   -4.91%     
==========================================
  Files         249      252       +3     
  Lines       47251    47496     +245     
==========================================
- Hits        27096    24906    -2190     
- Misses      16727    19406    +2679     
+ Partials     3428     3184     -244     

Impacted Files	Coverage Δ
creator/block.go	68.42% <70.58%> (+0.11%)	:arrow_up:
creator/polyline.go	81.81% <81.81%> (ø)
creator/rectangle.go	88.46% <85.71%> (+3.84%)	:arrow_up:
creator/poly_cubic_bezier_curve.go	86.04% <86.04%> (ø)
creator/polygon.go	86.95% <86.95%> (ø)
contentstream/draw/shapes.go	77.58% <96.34%> (+8.35%)	:arrow_up:
creator/creator.go	70.50% <100.00%> (+0.48%)	:arrow_up:
creator/paragraph.go	84.07% <100.00%> (+0.36%)	:arrow_up:
internal/jbig2/globals.go	0.00% <0.00%> (-100.00%)	:arrow_down:
internal/e2etest/memory_measure.go	0.00% <0.00%> (-100.00%)	:arrow_down:
... and 68 more

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[gunnsth]

This PR has been reviewed and integrated into newest UniPDF v3.11.0 release.