refactor documentation

[aaguinal]

This PR updates the documentation found on https://algebraicjulia.github.io/AlgebraicRewriting.jl/dev/.

More specifically, this:

• Provides a gentle overview of the package on the homepage
• Maintains the examples such that they are compatible with Catlab 0.16.5 and AlgebraicRewriting 0.3.0
• Compiles the library reference docs

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (fc2269a) 81.55% compared to head (4ab460d) 76.97%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #38 +/- ## ========================================== - Coverage 81.55% 76.97% -4.59% ========================================== Files 28 28 Lines 1681 1681 ========================================== - Hits 1371 1294 -77 - Misses 310 387 +77 ```

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[kris-brown]

also I suspect that src/generated should be added to the .gitignore

[kris-brown]

Looks great to me, thanks!