Add sitemaps to sites

[gndelia]

We need to add sitemaps to

• [ ] webapp

[rmilrad]

@gndelia Is this still needed?

[gndelia]

It is a low-priority issue, not needed, but it adds to the look and feel of the app.

This adds a "card" when sharing it on social media or similar.

See for instance when sharing this link in slack how it looks

It could be added to the get-started and to the tunnel itself