New LessWrong Editor! (Also, an update to our LLM policy.)

There's a new editor experience on LessWrong! A bunch of the editor page has been rearranged to make it much WYSIWYG compared to published post pages. All of the settings live in panels that are hidden by default and can be opened up by clicking the relevant buttons on the side of the screen. We also adopted lexical as a new editor framework powering everything behind the scenes (we were previously using ckEditor). That scary arrow button in the top-left doesn't publish your post! It just opens the publishing menu.