Improve link previews

[timmymmit]

Is your feature request related to a problem? Please describe.

When sharing a URL for a playground project, the link preview that is generated by various platforms (i.e Twitter, Slack, Reddit, etc) only contains generic metadata. This makes it difficult to create unique and sharable playground links.

Describe the solution you'd like

I would like to have the ability to specify a title (and maybe also a description) for my project. This title should be displayed in the link preview that is generated.

Seeing as each playground is generated with a random set of avatars, it would be great if these avatars were used to create an image that is included in the Open Graph metadata.

[bthaile]

Note:
Need to have server side rendering to build meta data before preview client gets it, since they don't execute javascript. Could convert playground to next.js app.