Add update option for embeddings

[NourOM02]

I read on the readme file that if the changes happen to the database then new embeddings are required. However, the user should manually go and delete the old embeddings. Therefore I thought that adding an update paramter to the load_embeddings function can make the process more automatic.

[rishsriv]

Thank you for the helpful PR! :)

[NourOM02]

The tests failed due to the sentence-transformers version conflicting with the huggingface-hub version (which is probably the latest since it isn't specified in the requirements file). The solution is to either upgrade the sentence-transformers package or downgrade the huggingface-hub package. I chose the first option and modified the requirements file. The tests run OK in my local machine.

[rishsriv]

Thanks - much appreciated!