feat: add configurable hotkeys to cycle tabs

Adds two configurable hotkeys (plus the required code infrastructure to
handle configurable hotkeys) for cycling the active chat tab forward by
one and backwards by one.

ChatTwo/GameFunctions/Chat.cs

@@ -266,6 +266,36 @@ internal sealed unsafe class Chat : IDisposable
                 modifierState |= modifier;
         }
 
+        bool KeyPressed(VirtualKey key, ModifierFlag modifier)
+        {
+            if (!Plugin.KeyState.IsVirtualKeyValid(key))
+                return false;
+
+            var modifierPressed = Plugin.Config.KeybindMode switch
+            {
+                KeybindMode.Strict => modifier == modifierState,
+                KeybindMode.Flexible => modifierState.HasFlag(modifier),
+                _ => false,
+            };
+
+            return modifierPressed && Plugin.KeyState[key];
+        }
+
+        // Test for custom keybinds for changing chat tabs before checking
+        // vanilla keybinds.
+        if (Plugin.Config.ChatTabBackward != null && KeyPressed(Plugin.Config.ChatTabBackward.Key, Plugin.Config.ChatTabBackward.Modifier))
+        {
+            Plugin.KeyState[Plugin.Config.ChatTabBackward.Key] = false;
+            Plugin.ChatLogWindow.ChangeTabDelta(-1);
+            return;
+        }
+        if (Plugin.Config.ChatTabForward != null && KeyPressed(Plugin.Config.ChatTabForward.Key, Plugin.Config.ChatTabForward.Modifier))
+        {
+            Plugin.KeyState[Plugin.Config.ChatTabForward.Key] = false;
+            Plugin.ChatLogWindow.ChangeTabDelta(1);
+            return;
+        }
+
         var turnedOff = new Dictionary<VirtualKey, (uint, string)>();
         foreach (var toIntercept in KeybindsToIntercept.Keys)
         {
@@ -281,20 +311,7 @@ internal sealed unsafe class Chat : IDisposable
 
             void Intercept(VirtualKey key, ModifierFlag modifier)
             {
-                if (!Plugin.KeyState.IsVirtualKeyValid(key))
-                    return;
-
-                var modifierPressed = Plugin.Config.KeybindMode switch
-                {
-                    KeybindMode.Strict => modifier == modifierState,
-                    KeybindMode.Flexible => modifierState.HasFlag(modifier),
-                    _ => false,
-                };
-
-                if (!modifierPressed)
-                    return;
-
-                if (!Plugin.KeyState[key])
+                if (!KeyPressed(key, modifier))
                     return;
 
                 var bits = BitOperations.PopCount((uint) modifier);

ChatTwo/GameFunctions/Types/ModifierFlag.cs

@@ -3,6 +3,7 @@ namespace ChatTwo.GameFunctions.Types;
 [Flags]
 internal enum ModifierFlag
 {
+    None = 0,
     Shift = 1 << 0,
     Ctrl = 1 << 1,
     Alt = 1 << 2,