Add link to documentation within PicoForge

[hanakomisa]

Before submitting a feature request, check the following checklist:

• I have searched the existing issues/discussions to ensure this hasn't been proposed before
• I have confirmed this feature is within the scope of PicoForge/LibreKeys
• I am using the latest version of PicoForge

Proposed Feature

Provide a link to the Librekeys documentation over at https://librekeys.github.io inside of PicoForge for easy access.

How would this improve the user experience?

This will make it easier to see the docs and help users getting set up.