Request: updated docs for IDE integration

[jfly]

I see we have a brief section on IDE integration in the README, but it only mentions isbecker/treefmt-vscode. I know there are other solutions (such as these two neovim solutions: none-ls's treefmt and none-ls's nix_flake_fmt).

My suggestion

• I'd like to see IDE integration documented somewhere on the website.
• I think there are actually 2 different things to document:
  • A guide for people who want to configure their editors to use treefmt.
  • A guide for people who want to build an IDE integration. Here we can debate interesting questions such as: how/if direnv should be involved, and how/if the the flakes specific nix fmt should be mentioned.

Additional context

Today, individual autoformatters feel the need to document this thing, and they often do it wrong (https://github.com/NixOS/nixfmt/issues/303). This is the sort of "solve it once" problem that I think treefmt is well suited for.