documize-community: init at 2.2.1

Documize is an open-source alternative for wiki software like Confluence
based on Go and EmberJS. This patch adds the sources for the community
edition[1], for commercial their paid-plan[2] needs to be used.

For commercial use a derivation that bundles the commercial package and
contains a `$out/bin/documize` can be passed to
`services.documize.enable`.

The package compiles the Go sources, the build process also bundles the
pre-built frontend from `gui/public` into the binary.

The NixOS module generates a simple `systemd` unit which starts the
service as a dynamic user, database and a reverse proxy won't be
configured.

[1] https://www.documize.com/get-started/
[2] https://www.documize.com/pricing/

nixos/modules/module-list.nix

@@ -739,6 +739,7 @@
   ./services/web-apps/atlassian/crowd.nix
   ./services/web-apps/atlassian/jira.nix
   ./services/web-apps/codimd.nix
+  ./services/web-apps/documize.nix
   ./services/web-apps/frab.nix
   ./services/web-apps/icingaweb2/icingaweb2.nix
   ./services/web-apps/icingaweb2/module-monitoring.nix