Add CMasher colormaps and update documentation

[andrew-saydjari]

Adding CMasher

[andrew-saydjari]

PR to address #142

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 50.75%. Comparing base (3693bff) to head (d250262).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/ColorSchemes.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #148      +/-   ##
==========================================
- Coverage   51.14%   50.75%   -0.39%     
==========================================
  Files           1        1              
  Lines         131      132       +1     
==========================================
  Hits           67       67              
- Misses         64       65       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[andrew-saydjari]

@cormullion can you let me know if this attempt looks good? I would like to be able to see the preview of the docs that were built by the CI here to confirm that they were imported correctly.

Also, as you predicted, there were some naming collisions. Specifically

┌ Warning: skipping copper
┌ Warning: skipping fall
┌ Warning: skipping neon
┌ Warning: skipping ocean
┌ Warning: skipping watermelon

To avoid this, and because I like having uniformity, I just made all of the names "cmr_*" for the scheme names as found in the CMasher repo.

[cormullion]

Don’t forget to import the new schemes:

ColorSchemes.jl/src/ColorSchemes.jl

Line 118 in 3693bff

function loadallschemes()