[MIRROR] Implementing tgchat to replace old VChat (#7371)

Co-authored-by: Heroman3003 <31296024+Heroman3003@users.noreply.github.com>
Co-authored-by: Selis <selis@xynolabs.com>

code/datums/chat_payload.dm

@@ -0,0 +1,16 @@
+/// Stores information about a chat payload
+/datum/chat_payload
+	/// Sequence number of this payload
+	var/sequence = 0
+	/// Message we are sending
+	var/list/content
+	/// Resend count
+	var/resends = 0
+
+/// Converts the chat payload into a JSON string
+/datum/chat_payload/proc/into_message()
+	return "{\"sequence\":[sequence],\"content\":[json_encode(content)]}"
+
+/// Returns an HTML-encoded message from our contents.
+/datum/chat_payload/proc/get_content_as_html()
+	return message_to_html(content)