chore: dead links removed

[maehr]

Remove dead links from the "Twitter" section.

Short pitch

• Mareike König moved her account from Twitter/X to Mastodon https://mastodon.social/@[email protected] I could not find the lists that she used to maintain and removed the dead links from the list.
• Link to Annoation Studio updated to https://github.com/hyperstudio/Annotation-Studio
• Link to AutoCat removed, tool is no longer maintained
• [ ] https://dhcenter-unil-epfl.com/ server name not resolvable
• [ ] https://dirtdirectory.org/ server name not resolvable
• [ ] http://tadirah.dariah.eu/vocab/ server name not resolvable
• [ ] https://digital.hssonline.org/ server name not resolvable
• [ ] https://vistorian.online/ server name not resolvable
• [ ] https://readcoop.eu/transkribus/?sc=Transkribus 403
• [ ] https://www2.unil.ch/ladhul/fr/home.html 404
• [ ] https://mith.umd.edu/chain/ 404
• [ ] http://dh101.humanities.ucla.edu/ timeout

Checklist

• [x] I have read and understood the contribution guidelines.
• [x] Table of contents has been updated (if a section is added / removed).
• [x] Contents have been sorted alphabetically.