make bliss pip installable

[ismael-mendoza]

add workflow to publish bliss when a new version is released

Misc

• Remove ToyGaussian as it it's no longer useful
• Update README to at least mention bliss is pip installable

[codecov]

Codecov Report

Merging #707 (12462c4) into master (baead54) will decrease coverage by 0.14%.
The diff coverage is 100.00%.

❗ Current head 12462c4 differs from pull request most recent head b513a7c. Consider uploading reports for the commit b513a7c to get more accurate results

@@            Coverage Diff             @@
##           master     #707      +/-   ##
==========================================
- Coverage   86.03%   85.88%   -0.15%     
==========================================
  Files          27       27              
  Lines        3809     3762      -47     
==========================================
- Hits         3277     3231      -46     
+ Misses        532      531       -1     

Flag	Coverage Δ
unittests	85.88% <100.00%> (-0.15%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
bliss/datasets/galsim_galaxies.py	94.52% <ø> (-1.34%)	⬇️
bliss/catalog.py	84.71% <100.00%> (+0.25%)	⬆️
bliss/models/prior.py	91.21% <100.00%> (ø)

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