Addon buttons that utilize middle click functionality for OnClick function from LDB are not able to use any buttons other than Left and Right Clicks since MBB overloads RegisterForClicks function with

Line: 348 MBB.lua:

	if( buttonframe ) then
		if( buttonframe.RegisterForClicks ) then
			buttonframe:RegisterForClicks("LeftButtonDown","RightButtonDown");
		end

Please modify to either AnyDown or at least for MiddleButtonDown which should cover most of the button cases for pretty much any addon.

Proposed change:

	if( buttonframe ) then
		if( buttonframe.RegisterForClicks ) then
			buttonframe:RegisterForClicks("LeftButtonDown","RightButtonDown","MiddleButtonDown");
		end

There's an edge-case that if someone doesn't have cvar ActionButtonUseKeyDown enabled, then no clicks will get passed to their addon minimap buttons as their 'action' is done on ButtonUp and MBB only has ButtonDown events handled... https://wowpedia.fandom.com/wiki/CVar_ActionButtonUseKeyDown
Though considering that it's always been ButtonDown... and folks don't complain... I don't have a strong opinion on including ButtonUp variations.