Add Windows-specific build docs (#68)

README.md

@@ -13,3 +13,19 @@ This repository hosts the source code of [v8.dev, the official website of the V8
 - `npm run build` builds the site into `dist`.
 - `npm run watch` builds the site into `dist` and watches for changes.
 - `npm start` kicks off a local HTTP server.
+
+### Additional Windows-specific instructions
+
+`npm run` might trigger Unix-specific commands. If you are using a Linux-like environment on Windows like git bash, msys2, or Cygwin, then you must configure npm to use it. This replaces the default behavior of using `cmd.exe`. For example:
+
+```sh
+npm config set script-shell "C:\\Program Files\\git\\bin\\bash.exe"
+```
+
+…or:
+
+```sh
+npm config set script-shell "C:\\msys64\\usr\\bin\\sh.exe"
+```
+
+You still need to run `npm` with a `PATH` that includes Linux utilities like `mkdir` and `rm`. Practically, it should work if you run `npm` from your Linux-compatible shell.