Added FastEmbed backend

[nickprock]

What does this PR do?

This PR add FastEmbed backend.

related to issue #2313

Before submitting

• This PR fixes a typo or improves the docs (if yes, ignore all other checks!).
• Did you read the contributor guideline?
• Was this discussed/approved via a Github issue? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes (if applicable)?
• Did you write any new necessary tests?

[MaartenGr]

This looks great! Thank you for the PR.

One thing that is missing is some documentation here to showcase how you can use those embeddings.

Also, note that we want to automatically select the embedding model as shown here rather than importing this backend. That removes another layer of complexity for the user.

[nickprock]

@MaartenGr thank you, I will do it as soon as possible

[MaartenGr]

Awesome, everything looks great. Thank you for taking the time to add this, it is greatly appreciated!