[Feature] Ability to update sparse index

[uahmad235]

Is this your first time submitting a feature request?

• I have searched the existing issues, and I could not find an existing issue for this feature
• I am requesting a straightforward extension of existing functionality

Describe the feature

Currently, we can only fit the sparse encoder once at the beginning. There should be an ability to update an existing index as more documents are added.

Describe alternatives you've considered

There are no straightforward alternatives. I've thought about creating a custom index that could allow updating existing index.

Who will this benefit?

This will benefit anyone who has continuous documents coming in (like users uploading documents). Especially when you do not have a set of enough documents in the beginning for fitting the encoder.
But as the pipeline begins, users can upload their org-specific documents and update their index.

Are you interested in contributing this feature?

Not currently

Anything else?

No response