build: add release-it to facilitate builds

[LoneRifle]

Problem

Releases are currently manual, tedious and prone to human error. While fully automated releases would be great, creating and maintaining such scaffolding would require planning. A much easier alternative would be to automate as much of the process for the publisher as possible

Closes #274

Solution

Port release scaffolding from passport-saml for consistent publishing across all repos in the node-saml organization

• npm install --save-dev release-it gren
• add release-it config and changelog run script from passport-saml

[cjbarth]

Are we going to release this on NPM using the @node-saml organization too, or will we continue with the package as it currently is on NPM? What we did with node-saml and passport-saml is we put up a deprecation notice for the unscoped packages and re-published under an NPM organization. It might make sense to do that here.

[LoneRifle]

@cjbarth It's up to you! We've just made one major release with breaking changes not too long ago, so we may as well rename the package (though we would have to copy over the DT types accordingly), since users will have to test before upgrading anyway.

[djaqua]

I'm on board with making releases easier. Also, do we have someplace where we can manage release goals or have a discussion about the direction of this project?

[LoneRifle]

@cjbarth @djaqua - I would like to have this PR merged so that we can move ahead with releases. As suggested, I will rename the package to @node-saml/xml-crypto

[cjbarth]

@LoneRifle , I made a few changes to this to use the latest package for generating changelogs and then added the first changelog. Have a look and LMK what you think. If you approve, I'll land it.

[LoneRifle]

Can't approve something I raise myself! Go ahead and merge.