:hammer: Add `mypy` Type Check to `stainnorm`, `stainaugment`, `patchextraction`

[Jiaqi-Lv]

Adds mypy checks to

• [x] tools/stainnorm.py
• [x] tools/stainaugment.py
• [x] tools/patchextraction.py

[codecov[bot]]

Codecov Report

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

Project coverage is 99.89%. Comparing base (ce348e7) to head (b297067). Report is 2 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #787 +/- ## ======================================== Coverage 99.89% 99.89% ======================================== Files 69 69 Lines 8534 8574 +40 Branches 1641 1641 ======================================== + Hits 8525 8565 +40 Misses 1 1 Partials 8 8 ```

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[shaneahmed]

@Jiaqi-Lv Please keep an eye on #786 as there might be a few conflicts.