Add module: Base64

[newswim]

closes #23
closes #44

Note:

• I diverted slightly from the validator.js module by making these url-safe by default. I don't have a great rationale for doing this, aside from it felt like the more correct general use-case. (Ended up adding a new module, Base64Url.
• This also contains some additional generated code that resulted from running yarn generate:schemables

Follow-up [edited]

• I learned quite a bit about Base64 encoding (and specifically RFC 4648), I think I'd like to follow up on this and potentially provide different modules that check that we're fully adhering to the spec.. but for now at least, this just follows the same checks provided by validator.js.

[jacob-alford]

👍 Great work, just a few comments to address, and question about possibly splitting base64 it up into different modules, or making the param non-optional

[jacob-alford]

💬 I'm open to optional params, but I ended up choosing against it for UUID because otherwise it doesn't make much sense why there's a function call for the combinator:

const User = SC.make(S => 
  S.struct({
    token: S.Base64()
  })
)

vs an explicit params, which make it clearer why it's a function call:

const User = SC.make(S => 
  S.struct({
    token: S.Base64({ urlSafe: true })
  })
)

And like you mentioned, an alternative for these simple configs would be to split them up into different modules

[newswim]

I ended up adding an additional module. I'll open a new issue to cover this. And it's probably worth discussing this some more since I expect we'll need to find out a middle ground between representing all possible variants, and having an API that is reasonably compact and appropriate for most use cases.

[newswim]

Created #44

[jacob-alford]

Beautiful 🎉