[Doc] Improve sidebar scrolling on headless docs

[slax57]

Problem

• Sidebar smooth scroll on first load is disturbing
• Sidebar scroll is happening even when the selected item is already into view

Solution

• disable scroll animation
• only scroll if element is not already into view

How To Test

make doc-headless

1. Access a page for the first time on a lower item (e.g. ListBase)
2. Navigate to another page using the sidebar menu
3. Navigate to another page using a link from within the doc content: e.g. navigate from <Resource recordRepresentation> to <RecordRepresentation>

Additional Checks

• The PR targets master for a bugfix or a documentation fix, or next for a feature
• The documentation is up to date

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