Add TF-IDF weights to tokens

[micheleriva]

This PR is still a work in progress. The algorithms are just POCs and highly inefficient, once we validate the idea, I'll proceed to optimize them.

[thomscoder]

Heyy, this is pretty neat! 💯 Especially for multi word searches.

I really like the idea.

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Will it be in symbiosis with tolerance ?

[micheleriva]

It shouldn't affect how typo tolerance work, but I really need to optimize this before trying 😄

[thomscoder]

I guessed, i really like the idea 😄

[micheleriva]

Closing this PR in favor of this Lyra plugin: https://github.com/LyraSearch/plugin-token-relevance