Add vscode via vendor package.

- Use yarn for vscode vendoring.
- Grab hash from package.

ci/build/build-vscode.sh

@@ -1,14 +1,15 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
-# Builds vscode into lib/vscode/out-vscode.
+# Builds vscode into vendor/modules/code-oss-dev/out-vscode.
 
 # MINIFY controls whether a minified version of vscode is built.
 MINIFY=${MINIFY-true}
 
 main() {
   cd "$(dirname "${0}")/../.."
-  cd lib/vscode
+
+  cd vendor/modules/code-oss-dev
 
   yarn gulp compile-build compile-extensions-build compile-extension-media
   yarn gulp optimize --gulpfile ./coder.js