Adds a Chat Reliability Layer (#79479)

## About The Pull Request

Everyone knows that chat will just eat your messages now and then, isn't
that annoying?
What if SSchat was smart enough to keep track of your messages and
notice when you didn't get one?
Well, now it can!
## Why It's Good For The Game

Chat messages poofing into the aether is bad, really bad.
## Changelog
🆑
add: Chat Reliability Layer
code: TGUI chat messages now track their sequence and will be resent if
the client notices a discrepenency
/🆑

---------

Co-authored-by: Kyle Spier-Swenson <kyleshome@gmail.com>

code/modules/tgui/tgui_window.dm

@@ -384,6 +384,8 @@
 			client << link(href_list["url"])
 		if("cacheReloaded")
 			reinitialize()
+		if("chat/resend")
+			SSchat.handle_resend(client, payload)
 
 /datum/tgui_window/vv_edit_var(var_name, var_value)
 	return var_name != NAMEOF(src, id) && ..()