I think I'm done with the documentation for this now.
I updated the page, including updating the example so that it uses a contenteditable div and therefore more input types can be observed more easily. I don't think we need to list all of the input types on the page, and can continue to just link to the spec section, which is fairly well written and understandable:
I have also submitted a PR to update the compat data for inputType to add a insertFromPasteAsQuotation sub-fearture:
https://github.com/mdn/browser-compat-data/pull/4104. Question - is insertFromPasteAsQuotation only supported in Firefox?
And I've tried to push forward on this PR that I submitted a while ago to add the Level 1 spec to MDN:
So that's it; let me know if you think anything else needs to be changed.