Removing warnings on Strict Mode and more

[elixs]

• Deleted leftovers from old context api (removes warning)
• Removed use of findDOMNode (removes warning)
• ScrollSyncPane "attachTo" now uses a reference (React.createRef or useRef)
• ScrollSyncPane "attachTo" can be changed dynamically
• ScrollSyncPane "enabled" can be changed dynamically
• ScrollSyncPane "attachTo" have priority over child component. If no "attachTo" is provided, a single child component with ref support is expected (for example a div or input, not a React.Fragment or more that one child)

[okonet]

I wonder how is this PR relevant since #74 has been merged.

[elixs]

I wonder how is this PR relevant since #74 has been merged.

This PR is built upon #74 because it left some code behind that shows a console warning (e2e441c)
Also I removed another console warning by replacing findDOMNode which is now deprecated.
And as I was fixing these warnings I also added support for changing the props attachTo and enabled at runtime (check componentDidUpdate from 772bd5c)

[okonet]

Okay thanks I got it now.

[github-actions]

🎉 This PR is included in version 0.11.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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