Add extraction of strings to be translated as part of build process

Add extraction of strings to be translated as part of build process for
ui_next.

Also, sets the source locale. See: https://lingui.js.org/tutorials/cli.html#configuring-source-locale

closes: https://github.com/ansible/awx/issues/7451

awx/ui_next/.linguirc

@@ -1,5 +1,6 @@
 {
    "localeDir": "src/locales/",
    "srcPathDirs": ["src/"],
-   "format": "po"
+   "format": "po",
+   "sourceLocale": "en"
 }