fix: new window for commonmark ref (#574)

https://zanata.atlassian.net/browse/ZNTA-1975

server/services/src/main/resources/messages.properties

@@ -351,7 +351,7 @@ jsf.SourceDocuments=Source Documents
 ! see related tooltip for more information about this action
 jsf.project.saveNotes=Save notes
 jsf.project.about.message=This section can be used to add notes for translators or other contributors to help answer questions or complete translations.
-jsf.project.about.markup=Notes are parsed as <a href="http://spec.commonmark.org/0.18/">CommonMark Markdown</a>
+jsf.project.about.markup=Notes are parsed as <a href="http://spec.commonmark.org/0.18/" target="_blank">CommonMark Markdown</a>
 jsf.project.EditHomePage.label=Edit Page Code
 jsf.project.EditHomePage.tooltip=Edit the Project's home page code as persisted. Useful when the home page cannot be edited via the project edit page.
 jsf.CreateVersion=Create Version