Show yaml parsing errors in hui-element-editor

[karwosts]

Proposed change

If there are yaml errors in a card editor, show those errors in the window.

Currently they are not shown, and if we click "Save", the window closes and any pending changes are lost. The only indication of an error is a red line on the side of the codemirror box, which is not always obvious to every user what it means.

This change shows yaml errors in the window, and disables the save button when there are yaml errors.

I have also elected to do a bit of debouncing on this detection, because if we just show the error immediately, it will show an error immediately every time a user types a keystroke on a new line, which I think is too aggressive.

So this only shows the error either after user pauses typing for 2 seconds, or when the codemirror box is blurred.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

[karwosts]

It's also possible that some of this error display should go directly into ha-yaml-editor itself, instead of being handled by every parent that instances one. Though in different contexts we may display errors in different ways or styles (e.g. fullscreen automation it is delivered by toast on save, vs ha-alert). Or we may need to respond to errors in different ways.