Add app/interfaces section

[razgraf]

Suggestion to add a new section including non-code documentation such as:

• tutorials (linking to youtube)
• a quick list of app features
• a "branding" section where we link the logo and other resources

[PaulRBerg]

Just to clarify - the suggestion is to add this new section in the top-left navbar, right?

[razgraf]

Solved in #56.