FR: add localization support to this extension

[GitMensch]

It looks like the standard way for vscode is json string replacement via https://github.com/microsoft/vscode-nls.

See https://github.com/microsoft/vscode-extension-samples/tree/master/i18n-sample how to integrate it. I won't recommend to use Transifex, instead just add the necessary infrastructure and let people PR to the new i18n directory providing the translations.