Produce strange filename for format javascript

[bsavelev]

Hello!

Try to use plugin with conf:

    new AngularGetTextPlugin({
          compileTranslations: { //optional
            input: 'locale/*.po',
            outputFolder: 'js/locale',
            format: 'javascript',
          },
    })

It produce es.javascript instead expected es.js
sa https://github.com/augusto-altman/angular-gettext-plugin/blob/master/index.js#L29

Is it a bug?