Add initial Renovate configuration

[renovate-rancher]

Add initial Renovate configuration, includes Renovate configuration file and GitHub Actions workflow. This automatically created PR has been initiated by @pjbgf

[pjbgf]

Given that the trigger is commented out, shall we simply delete this workflow instead?

[mallardduck]

Oh good catch - this is the only repo that matters now for this project. However it's a bit stuck in the past right now, so we haven't opted to enable cron. Hopefully when we catch up dependencies more and properly adopt branching strategy we can enable the cron.

[mallardduck]

I think we'll leave this around but consider it: "Blocked By: PromFed Repo Modernization Effort"
Which is currently waiting on a delicate game of Jenga with 4 major parts:

• Rebuild rancher-project-monitoring chart based on 0.3.4 #139
  • Not this one, but equivalent PRs on: https://github.com/rancher/ob-team-charts
• Update prometheus-federator to use dependencies from k8s 1.32.X+ #141
  • Not a blocker but will land before we have time to look into renovate
• [WIP][?/?] Adjust Charts Process #144 - replaced by following
  • [1/3] Adjust Charts Process: Remove rehomed charts #150
  • [2/3] Adjust Charts Process: Update CI scripts #151
  • [3/3] Adjust Charts Process: Add refactored PromFed Chart #152
• and "Adopt proper release based branches"

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Edit: Updated to reflect current state - we're not ready to enable it yet and from my testing today I know we have some configs that need modifying. This will be something I prioritize soon though once the current cycle to get 2.11 things ready is over. Or once we're more caught up on those tasks. 😄