docs: fix incorrect link to custom separator page

[jontze]

What is this PR about

This PR fixes the link to the custom separator page in the sidebar of the docs. Currently the link leads to a 404 - not found page. This was adjusted in this PR.

To test this locally:

• Run yarn serve-docs (docsify must be installed globally)
• Open http://localhost:3000
• Click on the Custom separator link in the sidebar

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows the guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)

[udayvunnam]

Thanks @jontze for updating the docs

[udayvunnam]

@all-contributors please add @jontze for doc

[allcontributors]

@udayvunnam

This project's configuration file has malformed JSON: .all-contributorsrc. Error:: Unexpected token } in JSON at position 1504

[udayvunnam]

@all-contributors please add @jontze for doc

[allcontributors]

@udayvunnam

This project's configuration file has malformed JSON: .all-contributorsrc. Error:: Unexpected token } in JSON at position 1504