Add ha-form-file element for file upload support in ha-form

[raulcodes]

Breaking change

Proposed change

Add support for file uploads in config flows.

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: Corresponding core PR
• 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

[bramkragten]

Why did you choose to add this to ha-form instead of using the file selector?

frontend/src/components/ha-selector/ha-selector-file.ts

Line 11 in d7da0d8

@customElement("ha-selector-file")

[raulcodes]

@bramkragten Because I didn't know that existed. Thanks for the feedback and callout! closing this as a no-op.