Missing charset labels

[sftse]

We've hit a charset label that is not recognized by this crate, but is recognized by encoding_rs. Upon further testing, there are 108 charset labels that are not recognized by mail-parser but are included in the encoding_rs crate.

l9
koi
utf8
koi8
sjis
ucs-2
ms932
utf-8
ascii
x-gbk
cp1250
cp1251
cp1252
cp1253
cp1254
cp1255
cp1256
cp1257
cp1258
visual
korean
x-sjis
ksc5601
gb_2312
dos-874
cn-big5
unicode
chinese
logical
koi8-ru
x-cp1250
ksc_5601
x-cp1251
iso88591
csgb2312
x-cp1252
iso88592
x-cp1253
iso88593
x-cp1254
iso88594
x-cp1255
iso88595
x-x-big5
x-cp1256
iso88596
x-cp1257
iso88597
x-cp1258
iso88598
iso88599
us-ascii
x-euc-jp
iso885910
iso8859-1
iso885911
iso8859-2
iso8859-3
iso885913
iso8859-4
iso885914
iso8859-5
iso885915
iso8859-6
iso8859-7
iso8859-8
iso-ir-58
iso8859-9
csunicode
iso8859-10
gb_2312-80
iso8859-11
hz-gb-2312
iso8859-13
iso8859-14
iso8859-15
iso-ir-149
big5-hkscs
windows-949
csisolatin9
csiso88596e
csiso88598e
unicodefffe
unicodefeff
csiso88596i
csiso88598i
windows-31j
x-mac-roman
iso-2022-cn
iso-2022-kr
csiso2022kr
replacement
iso-8859-6-e
iso-8859-8-e
iso-8859-6-i
sun_eu_greek
csksc56011987
unicode20utf8
unicode11utf8
ansi_x3.4-1968
x-mac-cyrillic
x-user-defined
csiso58gb231280
iso-10646-ucs-2
x-unicode20utf8
x-mac-ukrainian
iso-2022-cn-ext
unicode-1-1-utf-8

[sftse]

Some of these will not matter because of fallback to utf8: utf8, utf-8 and ascii, maybe others.

iso-8859-6-i is the one we hit in the wild.

[sftse]

The charset crate adds another three alternative labels for utf-7

x-unicode-2-0-utf-7
unicode-1-1-utf-7
csunicode11utf7