feat: add renovate bot

[chamburr]

This adds Renovate Bot to automate chart (and other dependency) updates, which will run as a GitHub Actions cron job and check for updates every hour. Expected results: https://github.com/chamburr/ocf-kubernetes/pulls

Todo

• Create labels on GitHub like this so that the bot can add them to the pull requests.
• Add a repository secret RENOVATE_TOKEN containing a personal access token of the GitHub user that will create the pull requests (perhaps https://github.com/ocfbot).
• Remember not to merge any pull requests involving Bitnami charts! All Bitnami charts will no longer work as of last month and will cause deployment errors!