Add some basic documentation for the Encoding role

Author: jnthn

doc/Type/Encoding.pod6

@@ -0,0 +1,51 @@
+=begin pod
+
+=TITLE role Encoding
+
+=SUBTITLE ...
+
+    role Encoding { ... }
+
+The C<Encoding> role is implemented by objects that provide a character
+encoding, such as ASCII or UTF-8. Besides being implemented by the built-in
+character encodings, it may also be implemented by users to provide new
+encodings. Instances of objects doing this role are typically obtained using
+C<Encoding::Registry>.
+
+=head1 Methods
+
+=head2 method name
+
+    method name({Encoding}:D: --> Str)
+
+Gets the primary name of the encoding.
+
+=head2 method alternative-names
+
+    method alternative-names({Encoding}:D: --> List)
+
+Gets a list of alternative names for the encoding.
+
+=head2 method decoder
+
+    method decoder({Encoding}:D: *%options --> Encoding::Decoder)
+
+Gets a character decoder instance for this encoding, configured with the
+provided options. Options vary by encoding. The built-in encodings all
+support C<translate-nl>, which if C<True> will translate C<\r\n> into
+C<\n> while decoding.
+
+=head2 method encoder
+
+    method encoder({Encoding}:D: *%options --> Encoding::Encoder)
+
+Gets a character encoder instance for this encoding, configured with the
+provided options. Options vary by encoding. The built-in encodings all support
+both C<replacement> (either a C<Str> replacement sequence or C<True> to use a
+default replacement sequence for unencodable characters) and C<translate-nl>
+(when set to C<True>, turns C<\n> into C<\r\n> if the current platform is
+Windows).
+
+=end pod
+
+# vim: expandtab shiftwidth=4 ft=perl6