fix: hide left sidebar scrollbar on long menus

[DanSchlachter]

Problem

When the left navigation menu content is longer than the viewport, a grey vertical scrollbar appears between the sidebar and the main doc area. It looks bad.

Change

Hide the scrollbar on .VPSidebar across all browsers (Firefox, legacy Edge/IE, Chrome/Safari) while keeping the sidebar scrollable via mouse wheel / trackpad.

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[chgeo]

Why do you think the scrollbar is bad here? It only appears when scrolling, so exactly when it's needed.
From an accessbility point I am not sure no scrollbars are desired. Check what the bast practises say here.

[DanSchlachter]

i think it looks really out of place there somehow, as it goes through the header area which isn't scrollable and is very dominant compared to the minimalistic style (especially on the internal docs page with changed layout).
There is also no scrollbar on the right page outline and I think this looks more modern.
But maybe that can be improved without removing it completely - especially if needed for accessibility

[chgeo]

The scrollbar is standard even in vitepress.dev:

it looks really out of place there somehow, as it goes through the header area

True for the header area, this is different compared to Vitepress.
So what about fixing this issue first?