Sanitize filenames in Ruby SDK

[davidenko87]

Describe the bug
We select files on their name, but we should also sanitize the names to prevent odd errors from the Transfer / Board endpoints

WeTransfer backend systems sanitize emojis (and control characters and special fs characters) from a file name. The sdk should do that as well, to bring that behavior closer to the end user, and have less surprises.

Expected behavior
We should sanitize the filenames and remove all characters that are lager then 4 bytes to prevent unforeseen errors with the Transfer endpoint

Possible Solution
filename.each_char.select{|c| c.bytes.count < 4 }.join('')