Chairbender Chat (#3794)

* #272 restructure and restyle chat line edit section

* #272 no arrow, actually change id on channel changer

* #272 nice round chat channel picker

* #272 add chat channel selection logic, and auto-select
when a prefix is entered

* #272 consistent width of chat channel btn

* #272 only show admin channel filter if asay perms

* #272 add tutorial info on chat prefixes

* #272 added chat filter button

* #272 added chat filter button

* #272 WIP on filter popup

* #272 fix filter popup pressed / unpressed logic

* #272 fix filter popup positioning and layout

* #272 WIP channel filter logic

* #272 WIP channel filter logic

* #272 WIP refactoring how chatbox / manager manages available filters and channels to send on

* #272 WIP implementing filtering UI / logic
and refactoring how chat UI is managed

* #272 fix various bugs with new chat filter / selector logic

* #272 remove outdated todos

* #272 WIP working chat window resize

* #272 bounded chatbox resizing

* #272 alertUI moves with resized chat

* #272 WIP making alertUI not be too large when changing size / UIScale

* #272 WIP fixing window / uiscale adjustment

* #272 WIP hacky approach for resizing, will try another approach

* #272 implement hacky approach for bounded chat resize

* #272 no resizing of lobby chat

* #272 WIP adding unread marker to chat filters

* #272 basic working unread chat message indicators

* #272 WIP adding horizontal channel selector items

* #272 horizontal channel selector popup

* #272 workaround for chat selector staying highlighted when right clicking it while toggled

* #272 workaround for chat selector staying highlighted when right clicking it while toggled

* #272 wip trying to add tests for chatbox

* #272 remove test, not really possible with current system

* #272 merge latest

* #272 merge latest

* #272 fix csproj changes

* It works if you disable the lobby

* Fixes lobby chat

* Adds more channel focusses

* Channel cycler

* Address review

* Address nitpicks

* Address more of the review

* Fix chat post-viewport

* Finalize review stuff

Co-authored-by: chairbender <kwhipke1@gmail.com>
Co-authored-by: ike709 <sparebytes@protonmail.com>

Content.Client/Chat/StoredChatMessage.cs

@@ -32,6 +32,11 @@ namespace Content.Client.Chat
         /// </summary>
         public Color MessageColorOverride { get; set; }
 
+        /// <summary>
+        /// Whether the user has read this message at least once.
+        /// </summary>
+        public bool Read { get; set; }
+
         /// <summary>
         ///     Constructor to copy a net message into stored client variety
         /// </summary>