Improve links in contentEncoding and contentMediaType

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

content/2020-12/content/contentEncoding.markdown

@@ -55,8 +55,13 @@ MIME header used in conjunction with the
 [`Content-Type`](https://www.rfc-editor.org/rfc/rfc2045.html#section-5) header
 to transmit non-ASCII data over e-mail. For example, if you send a PNG image as
 an e-mail attachment, your e-mail client will likely send a multipart message
-that includes the Base64-encoded image, sets the `Content-Transfer-Encoding`
-header to `base64`, and sets the `Content-Type` header to `image/png`.
+that includes the Base64-encoded image, sets the
+[`Content-Transfer-Encoding`](https://www.rfc-editor.org/rfc/rfc2045.html#section-6)
+header to
+[`base64`](https://datatracker.ietf.org/doc/html/rfc2045#section-6.1), and sets
+the [`Content-Type`](https://www.rfc-editor.org/rfc/rfc2045.html#section-5)
+header to
+[`image/png`](https://www.iana.org/assignments/media-types/image/png).
 
 {{</learning-more>}}
 

content/2020-12/content/contentMediaType.markdown

@@ -57,8 +57,13 @@ header used in conjunction with the
 [`Content-Transfer-Encoding`](https://www.rfc-editor.org/rfc/rfc2045.html#section-6)
 header to transmit non-ASCII data over e-mail. For example, if you send a PNG
 image as an e-mail attachment, your e-mail client will likely send a multipart
-message that includes the Base64-encoded image, sets the `Content-Type` header
-to `image/png`, and sets the `Content-Transfer-Encoding` header to `base64`.
+message that includes the Base64-encoded image, sets the
+[`Content-Type`](https://www.rfc-editor.org/rfc/rfc2045.html#section-5) header
+to [`image/png`](https://www.iana.org/assignments/media-types/image/png), and
+sets the
+[`Content-Transfer-Encoding`](https://www.rfc-editor.org/rfc/rfc2045.html#section-6)
+header to
+[`base64`](https://datatracker.ietf.org/doc/html/rfc2045#section-6.1).
 
 {{</learning-more>}}