Breakout from #516.

Once #984 is in, zizmor will have a (basic) LSP server mode via zizmor --lsp.

From there, there are a few obvious follow-ons:

• LSP mode should respect the user's config (relative to the workspace?)
• Supporting fixes/fix suggestions in the LSP? I'm not sure how annoying this will be to do.
• Supporting online audits in the LSP -- this is pretty easy to do in terms of code changes, but it'll be a lot slower than the current round-trip (which is almost instantaneous). Given that, it might make sense to make the current LSP implementation more incremental and fully leverage its asynchronicity.
• Per-editor integrations (like VS Code's "LSP client" extensions)
  • VS Code (Feature: IDE extensions #516) -- https://github.com/zizmorcore/zizmor-vscode
  • Sublime Text?
  • nvim?
  • Zed?