Add note to the example of Manifest Deployer

[pepsi1k]

Description

It’s unclear that the applier-manager picks up only files with the .yaml file type.

Fixes: #5481

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual test
• Auto test added

Checklist:

• My code follows the style guidelines of this project
• My commit messages are signed-off
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[juanluisvaladas]

Hi @pepsi1k, thanks for the contribution!

I think this is something we should document but not in the example section. I'd write it in the overview section... Maybe something like:

By default, k0s reads all manifest files under /var/lib/k0s/manifests that end with .yaml and ensures that their state matches the cluster state. It does not read files with other extensions, such as .yml. Moreover, on removal of a manifest file, k0s will automatically prune all of its associated resources.

Not necessarily exactly this, but somewhere around the overview section.