fix: layout shift [2607]

Created by: Tirokk

Authored by rbeer Mar 5, 2020 Merged Mar 10, 2020

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🍰 Pullrequest

This change

1. calculates the width of the vertical scrollbar (px-value)
2. sets px-value as padding-right to .main-navigation and body

thus preventing the page's content from shifting when filling up space that the disappearing scrollbar leaves behind.

Issues

• fixes #2607 (closed)
• relates #2564 (closed)

Remake of #3151