Update bug-management web page to reflect the new Inbox system

Instructions for bug triagers at https://inkscape.org/develop/bug-management/ need to be updated, too. We need a volunteer for this task who is familiar with bug triage and can come up with a suitable workflow.

Some preliminary updates are done to add the new link, etc. but the process explanations need revised. Whoever does the final update, please notify the translators mailing list when you are done.