Support 3.12 and drop 3.7

[codecov-commenter]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (e808fc8) 100.00% compared to head (a7d9b87) 98.16%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #99 +/- ## =========================================== - Coverage 100.00% 98.16% -1.84% =========================================== Files 5 5 Lines 381 381 =========================================== - Hits 381 374 -7 - Misses 0 7 +7 ``` | [Files](https://app.codecov.io/gh/gaogaotiantian/objprint/pull/99?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tian+Gao) | Coverage Δ | | |---|---|---| | [src/objprint/objprint.py](https://app.codecov.io/gh/gaogaotiantian/objprint/pull/99?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tian+Gao#diff-c3JjL29ianByaW50L29ianByaW50LnB5) | `100.00% <100.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/gaogaotiantian/objprint/pull/99/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tian+Gao)

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