Add token limit for uploaded files to the documentation

After spending quiet some time crafting and optimizing my knowledge file to be just under 512MB in size, I got a nasty surprise when trying to upload it and hitting the token limit of 2M tokens (which are roughly 7.5 MB in english plaintext).
Might be somewhere in the docs, but not at the relevant places like the File Docs and the Knowledge Retrieval Docs

Please add it.

Thanks for flagging, we added this to the assistants docs already and I just made a PR to add this to the API ref. Should be deployed soon!