Planetary.Link Support: Handle SSB URIs

[mplorentz]

Right now we only handle planetary.link URLs in Planetary. But we should also open the canonical SSB URI schemes that other apps support. This will allow users to open links to ssb messages and profiles that were generated by other apps.

[rabble]

This would be really great to do as manyverse generates them and i think that's the structure of room invites.

[rabble]

for rooms we support the ssbi uri's but we still need the other ones.

[boreq]

https://github.com/ssb-ngi-pointer/ssb-uri-spec

[mixmix]

the viewer is currently offline and not being developed (focusing on Room viewer first)

[boreq]

Related to https://github.com/joakim/ssb-qr