[1-min] add dependabot yaml

[newhouse]

Description of the change

Let's make it easier to keep this thing safe and up to date.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

Fixes #1

Checklists

Development

• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development
• No previous tests unrelated to the changed code fail in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached.
• At least one reviewer has been requested
• Changes have been reviewed by at least one other engineer
• The relevant project board has been selected in Projects to auto-link to this pull request