Improving PLS

[relf]

Added with PR #95, some improvements for PLS were identified during code review, they are listed here for reference:

• Add an example to the website
• Add benchmarks (should depend on Improving and extending benchmarks #103 )
• Use TruncatedSvd in PLS SVD implementations

[bytesnake]

first one already happened in f353d4d 😄

[relf]

Excellent! Didn't see the commit! Not only Rust is fast! 🚀

[relf]

Blocked by rust-ndarray/ndarray-linalg#274, waiting for fix in rust-ndarray/ndarray-linalg#275 to be released.