Symlink node_modules.asar to node_modules in lib/vscode

Closes #2197.

ci/dev/postinstall.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+main() {
+  cd "$(dirname "$0")/../.."
+  source ./ci/lib.sh
+
+  cd lib/vscode
+  yarn ${CI+--frozen-lockfile}
+
+  symlink_asar
+}
+
+main "$@"