Skerch

Fix

- updated method name

Feat

- Finished unit tests for added linops. All tests and precommits passing, ready to merge
- Added NoiseLinOp, SumLinOp, BandedLinOp. With docstrings

Fix

- Upgraded sigstore action, was also crashing CI

Feat

- Upgraded version of GH actions. Obsolete version was crashing CI

Fix

- Also updated readthedocs builder to 3.10 (doesn't affect code)

Feat

- Upgraded version requirements to python 3.10 and curvlinops >=2
- Implemented (sub-)diagonal and (block-)triangular sketched estimators (1)