Add compute_kernel

[MartinuzziFrancesco]

Adding the function compute_kernel, (named computeKernel on spyndex). To do list:

• Define the function and dispatch structure
• Add the kernel functions
• Dispatch on Dicts for numbers and arrays
• Dispatch on DataFrames
• Dispatch on YAXArrays
• Documentation
• Tests

[codecov]

Codecov Report

Attention: 18 lines in your changes are missing coverage. Please review.

Comparison is base (b206b8a) 79.58% compared to head (ec97ead) 74.46%.

Files	Patch %	Lines
src/compute_kernel.jl	68.88%	14 Missing ⚠️
src/compute_index.jl	84.61%	2 Missing ⚠️
src/utils.jl	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
- Coverage   79.58%   74.46%   -5.12%     
==========================================
  Files           5        6       +1     
  Lines         240      282      +42     
==========================================
+ Hits          191      210      +19     
- Misses         49       72      +23     

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