Add tests, reprs, docs, user-friendliness, etc. etc.

[Saransh-cpp]

• Closes #xxxx
• I am familiar with the
  contributing guidelines
• Tests added
• New code is fully documented. Includes compliant docstrings, examples, and
  comments where necessary.
• Pull request is nearly complete and ready for detailed review.

[codecov]

Codecov Report

Merging #27 (dbde32c) into main (f26ac75) will increase coverage by 3.86%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   93.75%   97.61%   +3.86%     
==========================================
  Files           3        3              
  Lines          80       84       +4     
==========================================
+ Hits           75       82       +7     
+ Misses          5        2       -3     

Impacted Files	Coverage Δ
riemapp/__init__.py	100.00% <ø> (ø)
riemapp/core.py	93.54% <60.00%> (-2.75%)	⬇️
riemapp/geometry.py	100.00% <0.00%> (+8.16%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more