Syntax completion for Janet and Fennel, small bug fixes, school improvements

Hello! I hope you've had a wonderful weekend so far! I'm about to go out for a run in the sun so I thought I'd release the current fixes and improvements from the develop branch first. I hope you enjoy!

• Use the syntaxcomplete#Complete omnifunc if the client isn't returning completions.
  • Janet and Fennel now have basic completion based on the syntax file.
  • It's hooked into omnicomplete seamlessly as well as all async completion frameworks that work with Conjure.
  • When you're in a Clojure buffer but you're not connected to an nREPL you'll also get syntax completion!
  • This is all configurable, see :helpg conjure#completion#omnifunc.
• Updated the sponsor list, welcome @aleksandersumowski!
• Sent out an update to all sponsors regarding sending of stickers 👀
• Internal fixes around maintaining the filetype for async function calls across filetype boundaries. Basically fixed some edge cases where evaluating something then changing to another unsupported filetype could cause issues.
• Worked out what's wrong with #111 (prompting for stdin for Clojure), haven't got a fix yet but it's understood now.
• Tested on nREPL 0.8.0, working fine! Will add support for the new completion and info ops soon!
• Improved a number of edge cases in the school, it should work consistently in any environment now 🤞
• Attempting to not load the client if we're in diff mode (like while sorting through git conflicts) for thirut on Discord. I don't think it's quite there yet, but it might improve some user's workflows considerably. Will probably be polished off in the next patch.

And that's all from me! I still have so much on my todo list that I want to get out very soon, hopefully you'll be seeing these very soon!

Have a great rest of your Sunday! Get some rest, look after yourself, see you soon!