Implement charset aliases

[Slamdunk]

The library doesn't take into account charset aliases:

transcoder/src/MbTranscoder.php

Lines 20 to 25 in e56652f

	if (null === self::$encodings) {
	self::$encodings = array_change_key_case(
	array_flip(mb_list_encodings()),
	CASE_LOWER
	);
	}

The library should take into account:

1. mb_encoding_aliases
2. https://wiki.mozilla.org/I18n:Charset_Aliases