feat: add dependabot

[nitrocode]

what

• Add dependabot

why

• The latest requests v2.31.0 resolves a CVE and this project uses an older requests in the requirements file
• Dependabot will autopropose PRs of dependencies that it detects to help keep dependencies up to date and make the project more secure
• Additional dependencies such as the python version of the project would be difficult to update using dependabot. For those cases, renovatebot should be evaluated.

https://github.com/cloudandthings/terraform-aws-clickops-notifier/blob/30f44815471751c442a14c674c794d76ebfbe99a/clickopsnotifier/requirements.txt#L3

references

• https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
• https://github.com/psf/requests/releases
• https://github.com/psf/requests/releases/tag/v2.31.0 (2023-05-22)
• https://github.com/psf/requests/releases/tag/v2.27.1 (2022-01-05)
• Closes https://github.com/cloudandthings/terraform-aws-clickops-notifier/issues/65

[baolsen]

LGTM, thanks for the contribution!