feat: add JS function to submit the language form

This was done to remove the HTML script later on

wger/core/static/js/language.js

@@ -0,0 +1,10 @@
+
+/**
+ * Submits the language form with the
+ * desired language code.
+ * @param {String} languageCode 
+ */
+function submitLanguageForm(languageCode){
+    document.getElementById('language-input').value = languageCode;
+    document.getElementById('language-form').submit();
+}