Support right to left override character

[dputtick]

• Closes Files with right-to-left override in filename should be marked dangerous #11 and Right-to-Left Override (RLO) character in filename Circlean#52
• Files with an rtlo character in the filename are now marked as dangerous and the character is stripped when copying to the destination key
• Adds an example file with an rtlo character in the filename to tests/src_invalid/

[codecov-io]

Codecov Report

Merging #13 into master will increase coverage by 0.22%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #13      +/-   ##
==========================================
+ Coverage   84.41%   84.64%   +0.22%     
==========================================
  Files           3        3              
  Lines         539      547       +8     
==========================================
+ Hits          455      463       +8     
  Misses         84       84

Impacted Files	Coverage Δ
bin/filecheck.py	78.11% <100%> (+0.54%)	✅

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