Made release script interactive to choose how to bump the version

[chandlerprall]

Moved the commands executed by yarn release out of the package's release script and into a ./scripts/release.js to enable additional functionality. I have tested the functionality up to the new git tag being pushed, but from that point on there are no changes compared to the previous release script.

CHANGELOG.md now auto-updates during a release
This is so the recent, un-published changes can be read by the release script, and so the new user-defined version can be injected when npm changes the package's version.

ensures user is on master branch

inspects CHANGELOG.md to recommend how to update the version, enforces the user's choice must be one of major, minor, or patch

if any steps fail, the release script is halted with an error code (this gif shows the script failing because the git working directory is dirty)

all stdout, stderr, and stdin pipes are passed as inherited, maintaining same output format as before

[snide]

"Your choice must be major, minor or patch"

Just to relate it specifically to the previous prompt.

[snide]

I tested this locally by manipulating a bunch of the changelog text. It'll obviously only be as good as we stick to pattern, but seems to work against a bunch of random ones I picked from the past.

I think once we merge this we should immediately run it to make sure the full npm process works (it looks like it should be fine), and we can always revert if it has trouble.

Might want a changelog item for this change itself. Know it's not directly consumer related, but feels big enough we'd want to mark it.