1475 prompt unicode characters

[PEZ]

What has Changed?

I've added default settings in the [clojure] scope for allowing the unicode characters that we use in the REPL prompt.

For now. I think we should entertain the option to instead render our prompt w/o unicode characters.

Fixes #1475

My Calva PR Checklist

I have:

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• Made sure I have changed the PR base branch, so that it is not published. (Sorry for the nagging.)
• Updated the [Unreleased] entry in CHANGELOG.md, linking the issue(s) that the PR is addressing.
• Figured if anything about the fix warrants tests on Mac/Linux/Windows/Remote/Whatever, and either tested it there if so, or mentioned it in the PR.
• [ ] Added to or updated docs in this branch, if appropriate
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