Provide a UI to easily customize the logo alternative text from the colorTheme

For context, the standard description "Logo of the wiki" is not very descriptive, and when the logo is customized it would basically always make sense to customize this to "Logo of XYZ", or even a concrete description of the logo. Therefore, I think this should be at the same place where the logo is configured in the sense of the Authoring Tool Accessibility Guidelines:

B.2.3.1 Alternative Content is Editable (WCAG):

If the authoring tool provides functionality for adding non-text content, then authors are able to modify programmatically associated text alternatives for non-text content.

While we have the ability to modify this translation, this is very hidden. Further, the guidelines also say:

B.2.3.2 Automating Repair of Text Alternatives:

The authoring tool does not attempt to repair text alternatives for non-text content or the following are all true: (Level A)

• (a) No Generic or Irrelevant Strings: Generic strings (e.g. "image") and irrelevant strings (e.g. the file name, file format) are not used as text alternatives; and

It seems far-stretched, but it could be argued that this alternative text is even too generic when the logo has been replaced.