Replace slashes in a name with `$slash` instead of `-`

[rintcius]

Description of the change

Previous behaviour cannot unambiguously unescape back to /. New behaviour improves this and is now in line with dotEscaper.

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Checklist:

• [x] Added the change to the changelog's "Unreleased" section with a link to this PR and your username
• [ ] Linked any existing issues or proposals that this pull request should close
• [ ] Updated or added relevant documentation in the README and/or documentation directory
• [x] Added a test for the contribution (if applicable)

[srghma]

:+1: