Add a feature to list all spelling errors in a project (or multiple projects)

### Description

NetBeans has a spellchecker, so it would be nice to have a way to list all spelling errors for the open project(s).

I don't know for now if it is better/easier to implement as a plugin.

As an idea, this might possibly use the `Actions Items` window just like some other features/plugins. In that case, the errors would be grouped under the category Spelling (other categories are TODO, Error, Checkstyle, etc.). Each error would be prefixed by something representing the location where it has been found. By example: "Javadoc comments: ", "HTML: ", "Properties: ", etc. It would be handled properly by the `Action Items Filter`, if one need to filter the list using some keywords. The `Next/Previous Error` under the `Navigate` menu would work as well, again just like other things like compiler errors.

Additionally, the spelling errors would be optionally highlighted on the vertical bar of the code editor.

For reference, I started a discussion about it here: #4247.

### Use case/motivation

I have a few projects where there is a bunch of spelling errors spread on a lot of files. In my case, this is in .java files (Javadoc comments). It is a time-consuming job to open each file and scroll to look for any spelling errors (red underlines). Having a summary in one place would be handy and make it an easier task in my opinion.

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow the Apache Software Foundation's [Code of Conduct](https://www.apache.org/foundation/policies/conduct.html)

Start with the discussion in #4247, then review how the Actions Items window, Action Items Filter, Next/Previous Error navigation, and editor vertical bar are described as possible integration points. Define the scope for scanning open projects and the supported content types before implementation; done should include a usable spelling-error summary and optional editor highlighting.

Written by the indexing model from the issue text.