Non-lowercase type aliases don't work

[raphinesse]

const sp = require('schemapack')
sp.addTypeAlias('edgeId', 'uint32')
sp.build('edgeId')

The code above will throw a this error:

TypeError: Invalid data type for schema: edgeId -> edgeid
    at getDataType (schemapack.js:22:51)
    at compileSchema (schemapack.js:349:24)
    at getCompiledSchema (schemapack.js:369:3)
    at Object.build (schemapack.js:382:21)
    ...

This happens because before lookup, aliases get lowercased but before creation, they don't. In the docs I could find no mention of type names having to be lowercase.

IMHO, the .toLowerCase() I linked above has to be removed.