`app-id` recommendation conflict with Flathub documentation

[lukors]

The official Flatpak docs have the following in its list of "examples of bad IDs" on this page:

• com.github.foo.Bar

  While a project may be hosted on GitHub it does not have any control over the github.com domain. Instead you should use io.github as shown above.

The elementary packaging documentation gives the following instructions:

Create a com.github.yourusername.yourrepositoryname.yml file in your project root with the following contents:

The elementary documentation recommends a practice which the Flatpak documentation explicitly lists as bad practice.

Suggested solutions

1. Make it recommend io.github instead of com.github.
2. Add a section explaining why using com.github isn't actually bad practice like it says in the Flatpak documentation.