Update WebKit2 dependencies

[freakboy3742]

Updates the unix pre-requisites to accomodate the WebKit2 package changes, primarily for the benefit of Ubuntu 24.04.

WebKit2 has been removed from the general Linux requirements list, in favor of a base set of packages plus an explicit list of system requirements on widgets that require it. The error message raised when those system requirements can't be found now explicitly references the system requirements in the docs (although the anchor on the link won't be valid until a stable release is cut).

Fixes #2544.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[rmartin16]

This looks really good. I added a few notes/corrections in line.

[rmartin16]

Good deal. I saw some additional opportunities to add details for OpenSUSE and align the specific list of reqs across the distros...but that seemed out of scope here. 👍🏼