Improve prepack script (#1747)

* improve prepack script

* remove .npmignore

* make prepack use pkg.files

* fix linter errors

scripts/prepack.sh

@@ -1,26 +0,0 @@
-#!/usr/bin/env bash
-
-# Configure to exit script as soon as a command fails.
-set -o errexit
-
-# Clean the existing build directory.
-rm -rf build
-
-# Create a temporary directory to place ignored files (e.g. examples).
-tmp_dir="ignored_contracts"
-mkdir "$tmp_dir"
-
-# Move the ignored files to the temporary directory.
-while IFS="" read -r ignored
-do
-  mv "contracts/$ignored" "$tmp_dir"
-done < contracts/.npmignore
-
-# Compile everything else.
-npm run compile
-
-# Return ignored files to their place.
-mv "$tmp_dir/"* contracts/
-
-# Delete the temporary directory.
-rmdir "$tmp_dir"