progress bar moves right to left for RTL books

[VallariAg]

resolves internetarchive/bookreader#580 Rotated the progress bar by 180 degrees for RTL books.

[codecov[bot]]

Codecov Report

Merging #615 (8ef7896) into master (e2a6a32) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #615   +/-   ##
=======================================
  Coverage   65.78%   65.78%           
=======================================
  Files          35       35           
  Lines        3761     3761           
  Branches      708      708           
=======================================
  Hits         2474     2474           
  Misses       1035     1035           
  Partials      252      252           

Impacted Files	Coverage Δ
src/js/BookReader/Navbar/Navbar.js	89.28% <ø> (ø)

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