Add vector_transform/pca binding

[pedramr]

Running example:

=== PCA Dimensionality Reduction Demo ===
Reducing from 64D to 3D

Training PCA...

Example transformation:
Original (first 5 of 64 values): [0.000 0.000 0.770 0.061 0.048 ...]
Transformed (3 values): [-4.993 -0.287 -0.445]

=== Similarity Search with PCA ===

Searching for neighbors of vector #500:
Nearest neighbors (ID: distance):
  #500: 0.0000
  #510: 0.0144
  #512: 0.0838

=== PCA with Whitening ===
Whitening normalizes variance (eigen_power=0.5)

[pedramr]

@abhinavdangeti @metonymic-smokey, was wondering if you'd be open to adding bindings outside of the index types that Bleve uses directly to go-faiss? Since they're very thin wrappers and can complement Bleve's use (e.g., using PCA to visualize a Bleve index content), adding them seemed directionally right, but let me know if you think otherwise. Thank you!

[metonymic-smokey]

@pedramr we definitely welcome contributions!
I'm not sure we can prioritise the ask right away though(@abhinavdangeti is the go-to here).

[pedramr]

Great, thanks! Yeah, agree that it probably doesn't make sense to add bindings for every Faiss method (if they won't be used, by "adding bindings" I just meant from contributions, on a per-need/incremental basis). I think this and #43 are pretty minimal wrappers that should make some lightweight visualization of a Bleve semantic index possible.

[pedramr]

@abhinavdangeti, wondering if you think might be worthwhile to add these bindings?