Add button that dismisses all notifications

[mattmattmatt]

Proposed change

Resolves this feature request that proposes a Dismiss All button in the notification list.

The new functionality adds a button at the bottom of the notification list that is only visible when there are 2 or more notifications. When pressed, a loop calls the persistent_notification.dismiss service on each notification, after which the notification drawer closes.

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: closes Dismiss All button in persistent notification sidebar #4983
• This PR is related to issue:
• Link to documentation pull request:

This is my first time working in HA Frontend, and also my first time working with Polymer/Lit. Please let me know of any best practices I may have missed and I'll be happy to amend the PR.

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

[homeassistant]

Hi @mattmattmatt,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!