👷 Add pip to dependabot config

[ff137]

Configures pip dependency management with dependabot

I've specified:

    schedule:
      interval: daily
    update-types:
      - "minor"
      - "major"
    commit-message:
      prefix: "chore(deps): "
    labels:
      - "dependencies"
      - "python"

Let me know if there are any desired changes.

update-types specifies to ignore patch releases, so it doesn't spam too much (and because ~ or ^ versioning already would include patch releases when lock file is updated)
Then, commit-message: prefix and labels is to match the existing dependabot PR style (which I assume is currently created manually)

[sonarcloud]

Quality Gate passed

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See analysis details on SonarCloud

[WadeBarnes]

Hi @ff137, We have one of our team members working on updating the dependabot configurations too. See his preliminary work for aca-py here; https://github.com/rajpalc7/aries-cloudagent-python/pull/1/files

[ff137]

@WadeBarnes good stuff! Thanks, that one's much more comprehensive 👍