Add bottom margin to button card icon

[spacegaier]

Breaking change

Proposed change

Currently there is no space between the icon and the label on a button card. On big buttons you do not see it since an MDI icon rarely fills up its box until the border. But if you define your icon to be smaller it is directly glued to the label. This PR now adds a bit of space.

Before:

After:

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