least squares examples

[AvanDavad]

These are simple least squares examples of how to apply a factor graph and how to use this codebase. This would have helped me a lot in understanding both the concepts and implementation. I was a bit confused first what Lie groups have to do with factor graphs... :)

[codecov[bot]]

Codecov Report

Merging #8 (51c381b) into master (076f825) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master       #8   +/-   ##
=======================================
  Coverage   93.22%   93.22%           
=======================================
  Files          29       29           
  Lines         930      930           
=======================================
  Hits          867      867           
  Misses         63       63           

Flag	Coverage Δ
unittests	93.22% <ø> (ø)

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

Impacted Files	Coverage Δ
jaxfg/geometry/_factors.py	100.00% <ø> (ø)

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[brentyi]

Thanks @AvanDavad!! Will try to get this merged soon, just gotta go through the typing/mypy errors. (which I can do)