fix: base64.py 'Incorrect padding' error

[Ciarands]

Fix:

Update python implementation of 'atob' to properly reflect behaviour of JS 'atob' by padding the base64 with "==".
https://stackoverflow.com/questions/2941995/python-ignore-incorrect-padding-error-when-base64-decoding

Motivation:

This fixes a number of JavaScript implementations for different Cryptography logic which takes advantage of atobs behavior, much of this logic doesn't take into account the padding, however Python's base64 library does.
Since padding is arbitrary we can append "==" to the string before decoding.
aGVsbG8gd29ybGQ -> raises binascii.Error
aGVsbG8gd29ybGQ= -> hello world
aGVsbG8gd29ybGQ== -> hello world
aGVsbG8gd29ybGQ=== -> hello world
and so on...

Examples:

Python - decode "hello world" no padding

import base64
data = "aGVsbG8gd29ybGQ"
base64.standard_b64decode(data)

binascii.Error: Incorrect padding

JavaScript - decode "hello world" no padding

atob("aGVsbG8gd29ybGQ")

'hello world'

Python - decode "hello world" with padding

import base64
data = "aGVsbG8gd29ybGQ"
base64.standard_b64decode(data + "==")

b'hello world'

[Xmader]

Thanks for the pull request!

[Xmader]

LGTM!
Thanks again for the pull request!