progress callback

[jeremybmerrill]

Would you be interested in a PR that would modify the existing logProgress option on BaseEmbedding to take a callback that gets called with the progress so far and the queue length.

This is useful for desktop apps where users might be shown a progress bar in the UI.

I see two ways to do it:

1. new progressCallback arg, deprecate logProgress: maintain logProgress (for now) its functionality (since the logProgress: true option would be superseded by progressCallback: (i, queue_length) => console.log(getting embedding progress: ${i} / ${queue.length});
2. change the type of logProgress to be a boolean or a function; if it's true, use the existing console.log.

I've used #1 (minus the deprecation of logProgress) here: https://github.com/jeremybmerrill/meaningfully/blob/feature/progress-bar/src/main/services/progressOpenAIEmbedding.ts

let me know if you want this, and I will send a PR (with tests).

[marcusschiesser]

great idea. we have in env package the Logger type: https://github.com/run-llama/LlamaIndexTS/blob/lee%2Fagent-step-handler/packages/env/src/logger/index.ts - maybe you use that?