refactor: Update script to generate schema JSON with 2 space indentation

[camdecoster]

Description

Update script to generate schema JSON with 2 space indentation.

Closes #7625.

Changes

• Update script
• Update schema

Testing

• Be on master
• Open test/plot-schema.json in a text editor
• Note that the indentation is 1 space per level
• Switch to this branch
• Run the schema build script with npm run schema
• Open the same file
• Note that the indentation is 2 spaces per level

Notes

• The schema file has a huge diff, but it's all white space
• You can turn off white space in the diff view with this option:
  

TODO

• Add draftlog

[emilykl]

Not totally sure whether we need a draftlog for this, but I don't mind

[emilykl]

Reasonable 👍

It does increase the file size from 3.6 to 4.2 MB. But if this file is used anywhere that the filesize actually matters, we should remove all whitespace anyway.