Update Compel documentation for textual inversions (#3663)

* Update Compel documentation for textual inversions

* Fix typo

Author: pdoane

docs/source/en/using-diffusers/weighted_prompts.mdx

@@ -94,5 +94,15 @@ a try!
 If your favorite pipeline does not have a `prompt_embeds` input, please make sure to open an issue, the 
 diffusers team tries to be as responsive as possible.
 
+Compel 1.1.6 adds a utility class to simplify using textual inversions.  Instantiate a `DiffusersTextualInversionManager` and pass it to Compel init:
+
+```
+textual_inversion_manager = DiffusersTextualInversionManager(pipe)
+compel = Compel(
+    tokenizer=pipe.tokenizer,
+    text_encoder=pipe.text_encoder,
+    textual_inversion_manager=textual_inversion_manager)
+```
+
 Also, please check out the documentation of the [compel](https://github.com/damian0815/compel) library for 
 more information.