docs: Tearing out README.fb.md and developers.fb.md

Summary:
These files were an insane assortment of mostly outdated stuff that duplicated itself and other things and have probably been written more often than read.

Make some new files with the relevant parts where LLMs and humans have a chance of discovering them. I've made an attempt to audit this a little bit. In some places I've just made the call to delete lots of stuff that seemed useless or harmful.

Much of this is very incomplete and this could use a lot of work, but at least this way we have a structure that we might be able to usefully expand on, compared to what we had before.

Reviewed By: IanChilds

Differential Revision: D102637372

fbshipit-source-id: 8800115ee0914b68ddd453b020c422e6f40a9185

Author: JakobDegen

vscode/README.fb.md

@@ -0,0 +1,45 @@
+### Starlark VS Code Extension
+
+Our team maintains a generic Starlark VS Code extension that gives IDE support
+for build files and .bzl files. It is under active development and will be
+gaining features regularly.
+
+There are two copies of the VS Code Extension. One is for internal use, and is
+at `fbsource/vscode/vscode-extensions/starlark`, and the other, for OSS use, is
+at `starlark-rust/vscode`.
+
+The key difference is that the internal version integrates with our internal
+VSCode infrastructure, and has some extra feature gating, interaction with the
+old buck extension, and uses our metrics framework. It also has some different
+setting defaults, like using `buck2` as the LSP binary instead of `starlark`
+
+This plugin works by talking to `buck2 lsp` over stdin/stderr. As features are
+implemented in buck2's LSP server, they will automatically start working in the
+plugin.
+
+If trying to build and install the OSS plugin on an eden FS, it can help to add
+a redirect to the vscode plugin's node_modules directory:
+
+```shell
+eden redirect add fbcode/buck2/starlark-rust/vscode/node_modules bind
+```
+
+To use the internal plugin for development, see the README in
+`fbsource/vscode/vscode-extensions/starlark`.
+
+To use the OSS plugin for development, follow the instructions at
+`starlark-rust/vscode/README.md`, or the abbreviated ones here.
+
+- `cd starlark-rust/vscode && npm install && npm install vsce && npm exec vsce package`
+- In VS Code, go to Extensions, click on the "..." button in the Extensions bar,
+  select "Install from VSIX" and then select the `starlark-1.0.0.vsix` file at
+  `$FBCODE/buck2/starlark-rust/vscode/starlark-1.0.0.vsix`
+- Update the extension settings to point to `buck2` for `starlark.lspPath`, and
+  `["lsp"]` for `starlark.lspArguments`. This can be done in the VS Code UI by
+  going to the extension's settings panel.
+
+If you want to use a local build of buck2, just change the path to
+`$FBCODE/buck2/scripts/buck2_lsp.sh` and unset `starlark.lspArguments`.
+
+NOTE: If you're seeing slightly confusing behavior, make sure that you're using
+"Starlark" as the language for files that you're editing.