v1.6.0: show tip if depot caching isn't detected

What's Changed

• add suggestion to use cache if no depot is detected by @IanButterworth in #41
  Disable with ignore-no-cache: true

Dep Updates

• Create dependabot.yml by @IanButterworth in #42
• Bump codecov/codecov-action from 1 to 3 by @dependabot in #45
• Bump actions/cache from 1 to 3 by @dependabot in #44
• Bump actions/setup-python from 2 to 4 by @dependabot in #43
• Bump actions/checkout from 2 to 4 by @dependabot in #46
• Bump actions/setup-python from 4 to 5 by @dependabot in #47

Full Changelog: v1.5...v1.6.0