Adds Fullscreen (#2878)

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## About The Pull Request
Added fullscreen as hotkey F11 and on OOC -> Toggle Fullscreen

![image](https://github.com/shiptest-ss13/Shiptest/assets/58084138/3db51657-c491-423a-a4e2-1e70647897b3)

![image](https://github.com/shiptest-ss13/Shiptest/assets/58084138/8136e422-922a-4937-8c59-50993d1a8bc1)


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## Why It's Good For The Game
You can play in fullscreen without annoying borders.
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benefit the game. If you can't justify it in words, it might not be
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## Changelog

:cl:
add: Fullscreen on F11
/:cl:

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code/__DEFINES/keybinding.dm

@@ -31,6 +31,7 @@
 #define COMSIG_KB_CLIENT_GETHELP_DOWN "keybinding_client_gethelp_down"
 #define COMSIG_KB_CLIENT_SCREENSHOT_DOWN "keybinding_client_screenshot_down"
 #define COMSIG_KB_CLIENT_MINIMALHUD_DOWN "keybinding_client_minimalhud_down"
+#define COMSIG_KB_CLIENT_FULLSCREEN_DOWN "keybinding_client_fullscreen_down"
 
 //Communication
 #define COMSIG_KB_CLIENT_OOC_DOWN "keybinding_client_ooc_down"

code/datums/keybinding/client.dm

@@ -45,3 +45,39 @@
 		return
 	user.mob.button_pressed_F12()
 	return TRUE
+
+/client
+	var/fullscreen = FALSE
+/datum/keybinding/client/t_fullscreen
+	hotkey_keys = list("F11")
+	name = "change_fullscreen"
+	full_name = "Toggle Fullscreen"
+	description = "Change window to Fullscreen or back"
+	keybind_signal = COMSIG_KB_CLIENT_FULLSCREEN_DOWN
+
+/datum/keybinding/client/t_fullscreen/down(client/C)
+	. = ..()
+	C.toggle_fullscreen()
+
+
+/client/verb/toggle_fullscreen()
+	set name = "Toggle Fullscreen"
+	set category = "OOC"
+
+	fullscreen = !fullscreen
+
+	if (fullscreen)
+		winset(usr, "mainwindow", "on-size=")
+		winset(usr, "mainwindow", "titlebar=false")
+		winset(usr, "mainwindow", "can-resize=false")
+		winset(usr, "mainwindow", "menu=")
+		winset(usr, "mainwindow", "is-maximized=false")
+		winset(usr, "mainwindow", "is-maximized=true")
+	else
+		winset(usr, "mainwindow", "titlebar=true")
+		winset(usr, "mainwindow", "can-resize=true")
+		winset(usr, "mainwindow", "menu=menu")
+		winset(usr, "mainwindow", "is-maximized=false")
+		winset(usr, "mainwindow", "on-size=fitviewport")
+
+	fit_viewport()