Add selectDefaultLanguage for publishes

This is useful when editing a publish, as it allows us to set the default language in the publish form to the language of the original claim

ui/component/publishAdditionalOptions/index.js

@@ -1,9 +1,22 @@
 import { connect } from 'react-redux';
+import { createSelector } from 'reselect';
 import { selectPublishFormValues, doUpdatePublishForm } from 'lbry-redux';
+import { selectIsStillEditing } from 'redux/selectors/publish';
 import PublishPage from './view';
 
+const selectDefaultLanguage = createSelector(
+  selectPublishFormValues,
+  selectIsStillEditing,
+  (publishState, isStillEditing) => {
+    const { languages, language } = publishState;
+    // returns the language of the original claim if editing
+    return isStillEditing ? languages[0] : language;
+  }
+);
+
 const select = state => ({
   ...selectPublishFormValues(state),
+  defaultLanguage: selectDefaultLanguage(state),
 });
 
 const perform = dispatch => ({

ui/component/publishAdditionalOptions/view.jsx

@@ -1,5 +1,5 @@
 // @flow
-import React from 'react';
+import React, { useEffect } from 'react';
 import classnames from 'classnames';
 import usePersistedState from 'effects/use-persisted-state';
 import { FormField } from 'component/common/form';
@@ -9,6 +9,7 @@ import Card from 'component/common/card';
 
 type Props = {
   language: ?string,
+  defaultLanguage: ?string,
   name: ?string,
   licenseType: ?string,
   otherLicenseDescription: ?string,
@@ -18,9 +19,21 @@ type Props = {
 };
 
 function PublishAdvanced(props: Props) {
-  const { language, name, licenseType, otherLicenseDescription, licenseUrl, updatePublishForm } = props;
+  const {
+    language,
+    defaultLanguage,
+    name,
+    licenseType,
+    otherLicenseDescription,
+    licenseUrl,
+    updatePublishForm,
+  } = props;
   const [hideSection, setHideSection] = usePersistedState('publish-advanced-options', true);
 
+  useEffect(() => {
+    updatePublishForm({ language: defaultLanguage });
+  }, []);
+
   function toggleHideSection() {
     setHideSection(!hideSection);
   }