Update localization.md

[qvarnstr0m]

Proposed documentation update to clarify the need for setting extension .json files as EmbeddedResource to ensure their inclusion during the build process in both development and production environments. This change aims to prevent issues with missing translations and improve localization reliability.

[CLAassistant]

All committers have signed the CLA.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.