Added Micro.blog icon

[rickcurran]

This PR adds a logo for the Micro.blog microblogging platform.

Logo was sourced via Manton Reece of Micro.blog here: https://help.micro.blog/2018/resources/

Please note I encountered some errors running npm run build so I hope all relevant files have been created for this additional logo.

[jasmussen]

Looks good 👍 👍

I could use a code sanity check, but otherwise this seems good.

[rickcurran]

Great, thanks!