Improve documentation of publishing plugins

[NyakudyaA]

Feature Description

Currently we have the following text

Requirements

    The plugin metadata contains a valid link to the homepage, the repository (source code), the tracker (issue tracker) and a license
    

I think we should improve the following

• The plugin metadata contains a valid link to the homepage(the URL should either point to a page describing plugin usage or the README/wiki in your repository), the repository (source code - should be publicly accessible and should not contain zipped files), the tracker (issue tracker) and a license.
• All plugins should include a short English description of what the plugin does.

Reference to Feature

No response