Do not require specifying the shasum when fetching source

[tas50]

If no shasum is provided the cookbook should attempt to fetch the SHASUMS.txt file, parse that file, and determine the shasum automatically. This would make it much easier to specify a version to install. We're doing this in the tomcat cookbook right now and it's working nicely.

[stephenreid]

I am using without a checksum, just version seems to fetch. I'm not sure that auto-fetching the checksum from the same domain at the same time adds any additional security (given nodejs.org hacked or dns poisoning.)

[github-actions]

Marking stale due to inactivity. Remove stale label or comment or this will be closed in 7 days. Alternatively drop by the #sous-chefs channel on the Chef Community Slack and we'll be happy to help! Thanks, Sous-Chefs.