Add myself to members.json

[hggeorgiev]

Hello

[XYQuadrat]

Hi Hristo! It's great that you want to join Polyring. As far as I can see, your site is quite empty so far. According to the guidelines on polyring.ch:

We generally only accept websites that already contain at least one bit of content beyond "First blog post" or "Hello world".

As such I will not yet merge this MR. Once you've added some content, just drop a comment here and I'll merge it :)