Differentiate vimiumHintMarker styles between opening in a new tab and the current tab

[JUSTIVE]

Currently, there’s only one design option for vimiumHintMarker, so when I accidentally press F instead of f, it’s hard to tell immediately whether the link will open in a new tab or the current tab.
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It would be great if there were more detailed class distinctions to allow different styles depending on whether the hint corresponds to a new-tab or same-tab action

This would make it much more intuitive to recognize which mode is active and reduce mistakes when using Vimium.

[JUSTIVE]

passing mode.name to classname will achieve this.
I'll make a PR for this.

[JUSTIVE]

close due to duplicated by #2049