Add "space-location" to the 'choose-elem-button' properties in the .add() function in LuaGuiElement

[Galdoc]

Under the properties for the .add() method of a LuaGuiElement, when type = 'choose-elem-button`, there should be mention of a property of "space-location", because otherwise buttons that use the elem_type of "space_location" won't be able to display on the button the icon for said location.

https://lua-api.factorio.com/latest/cla ... t.html#add

Side note -- It'd be cool if the fanned out property fields for the various GUI elements in the .add() function's documentation had little linky-doo buttons too.

[Therenas]

Rsed already added these, appreciate the report anyways!