fix help screen and cross hair

[bjarthur]

• [ x] I've built the docs and confirmed these changes don't cause new errors

the help screen and cross hair have been broken since opacity was changed to fill-opacity in GiovineItalia/Compose.jl#314. this PR fixes them.

[codecov-io]

Codecov Report

Merging #1251 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1251   +/-   ##
=======================================
  Coverage   85.74%   85.74%           
=======================================
  Files          35       35           
  Lines        4119     4119           
=======================================
  Hits         3532     3532           
  Misses        587      587

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