fix: Editors should support runtime configuration

Fetching settings directly via `process.env` circumvents the runtime
configuration mechanism.  Change the editor page to use `getConfig()`
instead.

src/editors/EditorContainer.jsx

@@ -2,6 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import { useParams } from 'react-router';
 import { EditorPage } from '@edx/frontend-lib-content-components';
+import { getConfig } from '@edx/frontend-platform';
 
 const EditorContainer = ({
   courseId,
@@ -13,8 +14,8 @@ const EditorContainer = ({
         courseId={courseId}
         blockType={blockType}
         blockId={blockId}
-        studioEndpointUrl={process.env.STUDIO_BASE_URL}
-        lmsEndpointUrl={process.env.LMS_BASE_URL}
+        studioEndpointUrl={getConfig().STUDIO_BASE_URL}
+        lmsEndpointUrl={getConfig().LMS_BASE_URL}
       />
     </div>
   );