Add abstract classes for quadrature rules

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Codecov Report

Attention: Patch coverage is 89.84375% with 13 lines in your changes missing coverage. Please review.

Project coverage is 94.33%. Comparing base (751a70b) to head (259c6d2).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6 +/- ## ========================================== - Coverage 95.74% 94.33% -1.41% ========================================== Files 7 7 Lines 540 530 -10 ========================================== - Hits 517 500 -17 - Misses 23 30 +7 ``` | [Files](https://app.codecov.io/gh/f0uriest/quadax/pull/6?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rory+Conlin) | Coverage Δ | | |---|---|---| | [quadax/\_\_init\_\_.py](https://app.codecov.io/gh/f0uriest/quadax/pull/6?src=pr&el=tree&filepath=quadax%2F__init__.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rory+Conlin#diff-cXVhZGF4L19faW5pdF9fLnB5) | `100.00% <100.00%> (ø)` | | | [quadax/quad\_weights.py](https://app.codecov.io/gh/f0uriest/quadax/pull/6?src=pr&el=tree&filepath=quadax%2Fquad_weights.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rory+Conlin#diff-cXVhZGF4L3F1YWRfd2VpZ2h0cy5weQ==) | `100.00% <100.00%> (ø)` | | | [quadax/adaptive.py](https://app.codecov.io/gh/f0uriest/quadax/pull/6?src=pr&el=tree&filepath=quadax%2Fadaptive.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rory+Conlin#diff-cXVhZGF4L2FkYXB0aXZlLnB5) | `96.87% <73.33%> (-3.13%)` | :arrow_down: | | [quadax/fixed\_order.py](https://app.codecov.io/gh/f0uriest/quadax/pull/6?src=pr&el=tree&filepath=quadax%2Ffixed_order.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rory+Conlin#diff-cXVhZGF4L2ZpeGVkX29yZGVyLnB5) | `91.96% <91.00%> (-1.52%)` | :arrow_down: |