Finished documenting the shards in linalg.cpp

[ShahFragcolor]

• Added/refined all the shards in linalg.cpp
• Removed the None type for the Flip Y parameter for Project and Unproject shards, gave it a default true instead if not set/
• Made Cross into a struct so that it can have specific help text.

[sinkingsugar]

You some compilation errors, redeclaring methods or so

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.80645% with 13 lines in your changes missing coverage. Please review.

Project coverage is 80.24%. Comparing base (1e7c174) to head (7478a66). Report is 15 commits behind head on devel.

Files	Patch %	Lines
shards/modules/core/linalg.cpp	81.69%	13 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## devel #1035 +/- ## ========================================== + Coverage 80.09% 80.24% +0.15% ========================================== Files 345 345 Lines 56569 57079 +510 ========================================== + Hits 45309 45805 +496 - Misses 11260 11274 +14 ```

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