changelog for v4.0.2

[bosesuneha]

This pull request releases version 4.0.2 of the k8s-set-context-action package. The update includes a new optional kubeconfig encoding variable and routine dependency updates.

Release and feature updates:

• Updated the package version to 4.0.2 in package.json to reflect the new release.
• Documented the addition of an optional kubeconfig encoding variable and dependabot dependency updates in CHANGELOG.md.