[frontend] map controls are selectable

[alxndrsn]

When dragging around a map, it's possible to start the drag in the wrong place and end up selecting the text of buttons.

Interestingly, the sibling element of these controls is the text "Showing 4 of 4", top-centre of the map. And this element does have user-select: none set:

Ideally all these controls would have user-select: none.

[matthew-white]

@latin-panda, I thought you might find this issue interesting as well. Maybe it applies to Web Forms as well? I'm planning to make this change in Central.

[latin-panda]

Thanks @matthew-white, We encounter this issue more frequently in iPhone, it's fixed. Maybe you can disable the context menu if that's more suitable for Central's use case, for example:

viewport.addEventListener('contextmenu', (e: Event) => e.preventDefault());