Update apps listings

[nathangathright]

• Remove "Sn-Network" and "Synchronize"
• Removing broken projects: Monbeam, CastCoverage, uSocial, Podvine
• Adding Seriously Simple Podcasting

[daveajones]

Thanks for this cleanup Nathan

[Marzal]

Hi, I was going to a make a PR to add SSP to the list, but I have found this one. Are you planing on merging?

Also I have found that SSP also supports:

• Podping: https://support.castos.com/article/276-enable-disable-podping
• Value: https://support.castos.com/article/408-seriously-simple-podcasting-settings-overview#Feed-Details-Settings-_WDlJ

And the appType could also indicate that is open source : https://gitlab.com/castos/Seriously-Simple-Podcasting

Good weekend 😉

[stevencrader]

I updated the PR to resolve the conflicts and made the changes suggested in #350 (comment)

@daveajones I'll let you merge this when you are ready to update the site.