Adds In-Game Link To Server Config (#94371)

## About The Pull Request

On the tin, just adds a link to
https://github.com/tgstation-operations/server-config to the game so
people are a little bit more aware of it.

Here's how it looks:

<img width="1386" height="275" alt="image"
src="https://github.com/user-attachments/assets/63d2d284-6d5f-4f41-ba80-abc33699f7c5"
/>

## Why It's Good For The Game

More visibility to a public resource, this wasn't feasible before the
present situation. It won't show up here unless the config variable is
set.
## Changelog
🆑
config: If you publicly host a copy of your server's config, you may now
link to the public URL in the 'CONFIGURL' setting in the server config.
It will show to players in the Escape Menu's Resources Carousel.
/🆑

code/controllers/configuration/entries/general.dm

@@ -330,6 +330,9 @@
 /datum/config_entry/string/githuburl
 	default = "https://www.github.com/tgstation/tgstation"
 
+/datum/config_entry/string/configurl
+	default = "https://github.com/tgstation-operations/server-config"
+
 /datum/config_entry/string/discordbotcommandprefix
 	default = "?"