Add Theory section on Docs

[sora-ryu]

This PR adds content on the Theory section, describing the overall workflow for Campbell Diagram generation organized by:

• Multi-Blade Coordinate (MBC) Transformation
• Eigenanalysis
• Mode Identification
• Mode Tracking via Assignment Problem
• Spectral Clustering

@deslaughter and @mayankchetan - Could you please review this updated documentation for the correctness and clarity? Thanks!

[deslaughter]

This looks great! I'd like you to add a couple of links to sources so users can get more details:

• MBC: https://docs.nrel.gov/docs/fy10osti/44327.pdf
• Similarity metrics: https://past.isma-isaac.be/downloads/isma2010/papers/isma2010_0103.pdf
• assignment problem: https://en.wikipedia.org/wiki/Assignment_problem
• hungarian algorithm: https://en.wikipedia.org/wiki/Hungarian_algorithm
• spectral clustering: https://arxiv.org/abs/0711.0189 and https://en.wikipedia.org/wiki/Spectral_clustering
• k-means clustering: https://en.wikipedia.org/wiki/K-means_clustering

This could be in a references section at the bottom or in each section, whichever you like.

[sora-ryu]

This looks great! I'd like you to add a couple of links to sources so users can get more details:

• MBC: https://docs.nrel.gov/docs/fy10osti/44327.pdf
• Similarity metrics: https://past.isma-isaac.be/downloads/isma2010/papers/isma2010_0103.pdf
• assignment problem: https://en.wikipedia.org/wiki/Assignment_problem
• hungarian algorithm: https://en.wikipedia.org/wiki/Hungarian_algorithm
• spectral clustering: https://arxiv.org/abs/0711.0189 and https://en.wikipedia.org/wiki/Spectral_clustering
• k-means clustering: https://en.wikipedia.org/wiki/K-means_clustering

This could be in a references section at the bottom or in each section, whichever you like.

Thanks for your review! The reference section is added now.