enhancement: #500 Flag for the ScrollSpy component that ensures the last active element remains visible + animationDuration option

[IvanPostu]

fixes #500

Proposed changes

Screenshots (if appropriate) or codepen:

Demo Video

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to change).

Checklist:

• I have read the CONTRIBUTING document.
• My commit messages follows the conventional commit format
• My change requires a change to the documentation, and updated it accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[wuda-io]

Nice, your video explaines it very clearly 👍 i will review the code tomorrow.

[wuda-io]

Please use more descriptive commit messages.
Also apply commit lint format so we can properly generate the changelog.
https://commitlint.io

[wuda-io]

Could you please also update the docs?
Please make a PR here https://github.com/materializecss/materialize-docs
Make sure you use the dev branch.