Improve k0s-in-docker docs

[bnallapeta]

Description

This PR improves the Docker setup documentation for k0s. It includes improved instructions for accessing the cluster locally, with guidance on configuring the kubeconfig file to work with localhost.

Fixes # (issue)

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

[jnummelin]

@bnallapeta DCO bot is not happy to see the first commit being not signed off properly. So pls rebase/squash the commits together, or edit the first one to have signoff and drop the last one.

Linter is not happy either:

Error: docs/k0s-in-docker.md:80:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 2; Style: 1/1/1]
Error: docs/k0s-in-docker.md:90:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 3; Style: 1/1/1]
Error: docs/k0s-in-docker.md:96:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 4; Style: 1/1/1]