Allow easier keyboard reading in custom drawers

[JKohlman]

Currently as it stands reading from the keyboard (Input.GetKeyDown, etc..) appears to be, at best, very difficult from a custom drawer without requiring a reference to ConfigurationManager.dll.

The main root of this lies in the config manager OnGUI at

BepInEx.ConfigurationManager/ConfigurationManager/ConfigurationManager.cs

Lines 273 to 274 in da2fc62

	if (!SettingFieldDrawer.SettingKeyboardShortcut)
	UnityInput.Current.ResetInputAxes();

which resets the keyboard inputs every frame. This is easy to work around in a global drawer by including ConfigurationManager.dll and simply setting SettingFieldDrawer._currentKeyboardShortcutToSet to your current SettingEntryBase.

BepInEx.ConfigurationManager/ConfigurationManager/SettingFieldDrawer.cs

Lines 27 to 28 in da2fc62

	private static SettingEntryBase _currentKeyboardShortcutToSet;
	public static bool SettingKeyboardShortcut => _currentKeyboardShortcutToSet != null;

HOWEVER, in a drawer that is not global and does not include ConfigurationManager.dll, the signature is:

static void CustomDrawer(BepInEx.Configuration.ConfigEntryBase entry)

And of course since the type is different you can no longer simply set that variable.

If there is an easy workaround that I'm missing I'd gladly make use of it but I can't seem to find one.