Make Widgetize page translatable #19076

The Widgetize page is currently hard coded in english: https://demo.matomo.cloud/index.php?module=Widgetize&action=index&idSite=1&period=day&date=yesterday

We should move all the English strings into translation files.

Related files:

• https://github.com/matomo-org/matomo/blob/793c7db0bec494d7165c60e04cbf4db5f701419b/plugins/Widgetize/vue/src/ExportWidget/ExportWidget.vue
• https://github.com/matomo-org/matomo/blob/793c7db0bec494d7165c60e04cbf4db5f701419b/plugins/Widgetize/vue/src/WidgetPreview/WidgetPreviewIframe.vue

follow-up to #19029