Add encoder for NonEmptyString

[d0liver]

Added an EncodeJson instance for NonEmptyStrings and a test for the EncodeJson and DecodeJson instances for NonEmptyStrings.

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Checklist:

• 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
• Added a test for the contribution (if applicable)

[thomashoneyman]

Don't worry about the CI failures related to dependencies -- these are due to breaking changes being made in the PureScript 0.14 package set.

[garyb]

I'd suggest adding a DecodeJson instance for it at the same time, I think all the encode/decodes are paired just now 🙂

[garyb]

Oh, sorry, I just saw on Slack there already is one!

[thomashoneyman]

@garyb This fixes a slip where we'd only added a DecodeJson instance for NonEmptyString and not included an encoder as well. So no need in this case, though in general you're spot on!

[thomashoneyman]

Ah, you're too fast for me!

[garyb]

Funny that we both noticed within seconds of each other, 2 hours after I commented 🤣