Adding "communities and organisations" category

The list is quite rich already, but there are some onion sites, which
don’t fall under the current categories.

I propose a “community and organisation” categories for associations,
organised communities.

I have added a hackerspace in Prague (both their clearweb and .onion
site) to this PR as an example of one such organisation.

I have including first-party "proof" url.

README.md

@@ -256,6 +256,14 @@ TBD
 
 ----
 
+# Communities and organisations
+
+## Brmlab, Prague Hackerspace
+  * http://pmwdzvbyvnmwobk5.onion/ onion site
+  * https://brmlab.cz/start clearweb site
+
+----
+
 # Submission Notes
 
 - **NO MORE THAN 1 SITE PER REQUEST WILL BE ACCEPTED**