Feature request: HTML, Separate the autocomplete from the spellchecker

### Description

Separate the autocomplete from the spellchecker, for HTML documents.

### Use case/motivation

Currently, or rather for several years now, the autocomplete and the spellchecker are fused together for HTML, so there is no way to disable one or the other. This means that in order to get spellcheck, any time you want to autocomplete, the first 9 options in the auto complete are plain text. You can disable this by turning the spellchecker off, but then the spellchecker is off, so you get no spellchecking, no red underlines.

What i want is to keep the spellchecker on, while disabling the autocomplete for plain text. I still want autocomplete on templates and functions, just not on plain text, i don't need dictionary words, especially not the first 9 in the list. Especially not words like "d'Arezzo's" or "d'Estaing's", which has to be the most uncommon words in the dictionary, when i want to make a div which shows up as the 10 option in the list.

There are people with dyslexia who program, i am one of them.

Simplest solution would just to let us pick how many words show up in the autocomplete, with the option for 0, or more then 9 for those who want that.

### Related issues

_No response_

### Are you willing to submit a pull request?

No

No files or tests are named. Start by locating the HTML editor's autocomplete and spellchecker integration, then inspect how their settings are exposed. Done means spellchecking remains available while plain-text dictionary suggestions can be disabled independently, without removing template or function completion.

Written by the indexing model from the issue text.