WIP: Support vector interpolation

[DanielVandH]

Solves #17.

• Fix existing tests
• Add tests for interpolation and differentiation of vector data
• Add suitable example to the docs, e.g. interpolating the solution to a PDE
• Figure out why things are randomly segfaulting. This could take a while since I have absolutely no clue why it's happening and have no MWE.
• Similar to above, figure out why things keep running forever.

[codecov]

Codecov Report

❌ Patch coverage is 76.21951% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.24%. Comparing base (eb2f856) to head (f473a31).
⚠️ Report is 39 commits behind head on main.

Files with missing lines	Patch %	Lines
src/differentiation/methods/direct.jl	54.16%	11 Missing ⚠️
src/differentiation/methods/iterative.jl	47.61%	11 Missing ⚠️
src/differentiation/differentiate.jl	63.63%	4 Missing ⚠️
src/utils.jl	75.00%	4 Missing ⚠️
src/data_structures/derivative_cache.jl	75.00%	2 Missing ⚠️
src/interpolation/coordinates/sibson.jl	81.81%	2 Missing ⚠️
src/data_structures/interpolant.jl	88.88%	1 Missing ⚠️
src/differentiation/generate.jl	93.33%	1 Missing ⚠️
src/interpolation/coordinates/farin.jl	88.88%	1 Missing ⚠️
src/interpolation/coordinates/hiyoshi.jl	96.15%	1 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #32      +/-   ##
==========================================
- Coverage   98.00%   95.24%   -2.76%     
==========================================
  Files          22       22              
  Lines        1200     1242      +42     
==========================================
+ Hits         1176     1183       +7     
- Misses         24       59      +35     

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