Adds Dangerzone Plugin

[akaalias]

Hi @lishid,

I'd like to submit my Dangerzone Writing plugin (See https://forum.obsidian.md/t/dangerzone-flowstate-like-plugin-prototype/8776) for details with this PR.

Let me know if this is okay!

Thank you,

Alexis

[lishid]

Couple of suggestions:

• Auto format your code so your spacing is consistent and semicolon is all added.
• Clear the setInterval when your plugin unloads. Probably want to cleanup the whole countdown object.
• I would suggest not storing all codemirror editors as a reference, because you're inducing a memory leak when panes are closed but you're holding on a reference to it.
  https://github.com/akaalias/dangerzone-writing-plugin/blob/ad53097930e79a551bd4067023fae72d142048c1/main.ts#L10
  Instead, your handleKeyDown function could unhook itself if the plugin has been disabled.