feat: Add BufferFromBase64 codec

[pasalino]

I propose to add this codec. It is useful when you have a base64 string from external of your domain.
In this case, mainly if the string is long, it is very useful to use a Buffer instead of a string for at least two reasons:

• if you have a base64 string and you move it within your domain, you copy the string many times, instead with Buffer you have a reference to pass between applications;
• in this way you already parse a base64 string and you are sure that Buffer contains a valid array of bytes. Of course, you cannot be sure of the correctness of the contents, but you are sure of the correctness of the base64 string.

import { BufferFromBase64 } from 'io-ts-types/lib/BufferFromBase64'
import { right } from 'fp-ts/lib/Either'

const base64String = 'dGVzdCBvZiB0aGUgY29kZWM='
assert.deepStrictEqual(BufferFromBase64.decode(base64String), right(Buffer.from('test of the codec')))