Add JSONPath scalar type and codec support

[slaskis]

Description

I have been patching postgraphile to add support for jsonpath and thought it might make sense to add upstream.

Performance impact

unknown, negligible I would presume since it just adds a codec

Security impact

Checklist

• [ ] My code matches the project's code style and yarn lint:fix passes.
• [ ] I've added tests for the new feature, and yarn test passes.
• [ ] I have detailed the new feature in the relevant documentation.
• [ ] I have added this feature to 'Pending' in the RELEASE_NOTES.md file (if one exists).
• [ ] If this is a breaking change I've explained why.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 6ed23307dfdb22be396e940fb251049e525d40c6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
graphile-build-pg	Patch
postgraphile	Patch
@dataplan/pg	Patch
graphile-utils	Patch
pgl	Patch
graphile	Patch

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[slaskis]

Great review thanks! 🙏 i was unable to get it to build and test (unrelated to this PR) but i’ll have another go at it later this week.

[slaskis]

All right, I managed to get the build and tests to run in an Ubuntu VM so it's looking a lot better now!

A few whitespace changes snuck in, if you want me to revert those let me know!