[Scrollbar] Restyle

[egekorkan]

This could be a bit higher priority even if it doesn't seem like it. In the current state, the scrollbar falls back to GUI Framework that electron is using on the given platform. In macOS and Windows it might always be the same but in Linux, Ubuntu users might fall back to Gnome style, KDE users fall back to KDE style etc. This results in scrollbars appearing in and around text areas that the wade developer does not see in his/her environment