Re-add snippet placeholder nodespecs

[piemonkey]

Overview

These commits were in futurenow after #653 was merged, but are no longer there or in master.

As far as I can tell from examining the git history, these are the only commits that are missing.

connected issues and PRs:

#653

Setup

N/A

How to test/reproduce

Snippet placeholders work correctly in Regulatory statements.

Challenges/uncertainties

It wasn't clear what rebase erased these commits, so the analysis was manual. I suggest git push --force-with-lease for anyone push-forcing to avoid this in the future.

Checks PR readiness

• UI: works on smaller screen sizes
• UI: feedback for any loading/error states
• Check cancel/go-back flows
• Check database state correct when deleting/updating (especially regarding relationships)
• changelog
• npm lint
• no new deprecations

[lagartoverde]

Looks good to me, it's basically the same thing I did in my branch