Fix typos in README file

[pitmonticone]

Fixed typos.

[codecov[bot]]

Codecov Report

Merging #452 (50ae628) into master (ae934bd) will decrease coverage by 1.51%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #452      +/-   ##
==========================================
- Coverage   78.02%   76.51%   -1.52%     
==========================================
  Files          23       23              
  Lines        1611     1571      -40     
==========================================
- Hits         1257     1202      -55     
- Misses        354      369      +15     

Impacted Files	Coverage Δ
src/io.jl	52.94% <0.00%> (-15.67%)	:arrow_down:
src/eventloop.jl	53.70% <0.00%> (-12.97%)	:arrow_down:
src/setup.jl	71.42% <0.00%> (-4.71%)	:arrow_down:
src/render.jl	88.57% <0.00%> (-1.43%)	:arrow_down:
src/methods.jl	67.82% <0.00%> (-0.35%)	:arrow_down:

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