feat(presets/custom-managers): Add Makefile custom manager preset

[phil9909]

Changes

Add a custom manager preset for Makefiles very similar to existing custom manager presets:

# renovate: datasource=node depName=node versioning=node
NODE_VERSION=18.13.0
# renovate: datasource=npm depName=pnpm
PNPM_VERSION = "7.25.1"
# renovate: datasource=npm depName=yarn
YARN_VERSION := '3.3.1'
# renovate: datasource=custom.hashicorp depName=consul
CONSUL_VERSION ?= 1.3.1

Context

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

The documentation for custom manager preset is auto-generated, right?

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[phil9909]

Thanks for the fast approval. How do we continue from here?

Should I update the branch?
Do features require multiple reviews?
Or is this ready to merge?

This is my first time contributing here. So I'm not sure how you handle such things, sorry.

[rarkins]

I was waiting in case there were other reviews, but I think it's fine to merge as it's opt-in. No need to update from main - it will be tested against a merge commit now before merging

[renovate-release]

🎉 This PR is included in version 37.411.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)
• 37.411.0

Your semantic-release bot 📦🚀