fix/set saved simplification

[joshua-dean]

Simplification of set_saved for submit buttons

Description

Closes #119. Between this and event listeners being in the .ulabel group, implementers of the tool should have full control over the reload prompt.

I left set_saved as optional in the type, as the SubmitButtons toolbox item will set the default regardless.

tl;dr is set_saved on submit buttons now defaults to "false". If set to "true", it will call ULabel.set_saved, skipping the reload/nav prompt.

PR Checklist

• Merged latest main
• Version number in package.json has been bumped since last release
• Version numbers match between package package.json and src/version.js
• Ran npm install and npm run build AFTER bumping the version number
• Updated documentation if necessary (currently just in api_spec.md)
• Added changes to changelog.md

Breaking API Changes

Technically the ability to make a submit button invalidate existing changes and force the reload prompt is gone.
If anyone was leveraging this functionality, let me know and I'll personally implement a feature to invalidate the save state on submit.