Add a wrapper script to keep ./solcjs available until we can drop it in a breaking release

Author: cameel

solcjs

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+[[ -e dist/solc.js ]] || npm run build
+exec dist/solc.js "$@" < /dev/stdin