[WIP] HGNNConv layers

[punnaamorn]

Description

Based on the existing python HGNN Conv layer, I changed that into Julia

I don't know why it says there is some changes in split function but I did not changed anything after I merge it from main. This pull request should be only the layer.jl folder

Include a short and descriptive summary of the changes here and the purpose of this PR (e.g., the issue this PR resolves, or the reason it was needed/desirable).

Dependency and version changes

List any (new) dependencies that are required for this change and any package versions that change in order for this PR to work.

Change features

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactor (change, which could be breaking or non-breaking, that mainly involves reorganizing code)
• This change requires a documentation update
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other (please describe below)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have run tests locally, and all tests passed
• My changes generate no (new) warnings

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 269 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.10%. Comparing base (a9c7f77) to head (e3622e4).

Files with missing lines	Patch %	Lines
src/core/transform.jl	0.00%	250 Missing ⚠️
src/core/layers.jl	0.00%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #10      +/-   ##
==========================================
- Coverage   62.58%   55.10%   -7.48%     
==========================================
  Files           8        9       +1     
  Lines        1983     2252     +269     
==========================================
  Hits         1241     1241              
- Misses        742     1011     +269     

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