add gh-pages deployment CI script - Fix #461

[WebFreak001]

See
https://github.com/WebFreak001/libdparse/actions/runs/3254075332
and generated gh-pages
https://github.com/WebFreak001/libdparse/tree/gh-pages

[codecov]

Codecov Report

Merging #468 (ddc0664) into master (55b2903) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #468   +/-   ##
=======================================
  Coverage   83.17%   83.17%           
=======================================
  Files          11       11           
  Lines        8338     8338           
=======================================
  Hits         6935     6935           
  Misses       1403     1403           

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[WebFreak001]

@rikkimax or @Geod24 can you enable github pages in the repository settings to the gh-pages branch so that we can use the generated pages from this PR?

[Geod24]

It was already enabled. I removed the custom domain which was pointing to netlify though.