finish training docs
* initial score_sde_ve docs * fixed typo * fix VE term
* up * up * finish
* uP * better * up * finish * up
* Update text_inversion.mdx Getting in a bit of background info * fixed typo mode -> model * Link SD and re-write a few bits for clarity * Copied in info from the example script As suggested by surajpatil :) * removed an unnecessary heading