! Don't disable the WYSIWYG editor in IE11

This is the only obvious place where explicit IE11 detection is needed, at least for now. Note that this change also doesn't stop IE from being identified as Gecko because that doesn't seem to break anything. Detection for IE11 will be added to the browser detection class in the near future.

Signed-off-by: Michael Eshom <oldiesmann@oldiesmann.us>