Noissue - Print publicSuffixList.json SHA-256 digest

In code reviews for publicSuffixList.json we need to verify that the submitter and the reviewer are both getting the same output. This is to defend against any potential man-in-the-middle situations (e.g. compromised software). One way to do the verification is to compare the output files. A much easier way is to compare SHA-256 digests.

This patch to build/updatepsl.js makes the script print the SHA-256 digest of the file before it is written out to disk.