[PROPOSAL] Move core validators to separate TS library

[snewcomer]

Similar to the work that went into ember-changeset, we can extract the core validators to a general typescript/javascript library. This necessitates looking at how we can generalize ember-validators to the greater JS community as well. I suspect this work would be relatively simple and would pair well with the new validated-changeset library.

https://github.com/validated-changeset/validated-changeset

[sandstrom]

While I understand the idea, I actually think it would be better to go in the opposite direction.

For certain open-source projects, it makes sense to abstract things away and turn the project into a building-block for others. But there are also a lot of costs associated with that path. More complexity, more work to maintain, higher threshold for new contributors, etc.

Somewhat related, I'd suggest inlining validated-changeset instead:

#306