feat: add PARAGON_THEMES_URL to the env files

Author: dcoa

.env

@@ -33,3 +33,5 @@ MFE_CONFIG_API_URL=
 PASSWORD_RESET_SUPPORT_LINK=''
 LEARNER_FEEDBACK_URL=''
 SUPPORT_URL_TO_UNLINK_SOCIAL_MEDIA_ACCOUNT='https://help.edx.org/edxlearner/s/article/How-do-I-link-or-unlink-my-edX-account-to-a-social-media-account'
+# Fallback in local style files
+PARAGON_THEME_URLS={}

.env.development

@@ -34,3 +34,5 @@ MFE_CONFIG_API_URL=
 PASSWORD_RESET_SUPPORT_LINK='mailto:support@example.com'
 LEARNER_FEEDBACK_URL=''
 SUPPORT_URL_TO_UNLINK_SOCIAL_MEDIA_ACCOUNT='https://help.edx.org/edxlearner/s/article/How-do-I-link-or-unlink-my-edX-account-to-a-social-media-account'
+# Fallback in local style files
+PARAGON_THEME_URLS={}