Fix a few typos in the documentation

[bryanwweber]

Thanks for the awesome library! I found a few small typos while learning to use the package 😄

[codecov[bot]]

Codecov Report

Merging #173 (1f24ab0) into master (1d135cd) will increase coverage by 0.10%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #173      +/-   ##
==========================================
+ Coverage   71.25%   71.35%   +0.10%     
==========================================
  Files          31       31              
  Lines        5180     5293     +113     
==========================================
+ Hits         3691     3777      +86     
- Misses       1489     1516      +27     

Impacted Files	Coverage Δ
src/drawings.jl	63.88% <0.00%> (-0.30%)	:arrow_down:
src/arrows.jl	90.82% <0.00%> (-0.27%)	:arrow_down:
src/text.jl	91.37% <0.00%> (-0.18%)	:arrow_down:
src/graphlayout.jl	0.00% <0.00%> (ø)
src/readshapefiles.jl	0.00% <0.00%> (ø)
src/juliagraphics.jl	98.64% <0.00%> (+<0.01%)	:arrow_up:
src/shapes.jl	94.77% <0.00%> (+0.03%)	:arrow_up:
src/noise.jl	47.91% <0.00%> (+0.07%)	:arrow_up:
src/curves.jl	93.77% <0.00%> (+0.11%)	:arrow_up:
src/bezierpath.jl	57.55% <0.00%> (+0.16%)	:arrow_up:
... and 9 more

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[cormullion]

Thanks!