Added docs on base64 only working with utf8 content

Author: mikefarah

pkg/yqlib/doc/operators/encode-decode.md

@@ -25,7 +25,7 @@ See CSV and TSV [documentation](https://mikefarah.gitbook.io/yq/usage/csv-tsv) f
 XML uses the `--xml-attribute-prefix` and `xml-content-name` flags to identify attributes and content fields.
 
 
-Base64 assumes [rfc4648](https://rfc-editor.org/rfc/rfc4648.html) encoding. Encoding and decoding both assume that the content is a string.
+Base64 assumes [rfc4648](https://rfc-editor.org/rfc/rfc4648.html) encoding. Encoding and decoding both assume that the content is a utf-8 string and not binary content.
 
 ## Encode value as json string
 Given a sample.yml file of:

pkg/yqlib/doc/operators/headers/encode-decode.md

@@ -25,4 +25,4 @@ See CSV and TSV [documentation](https://mikefarah.gitbook.io/yq/usage/csv-tsv) f
 XML uses the `--xml-attribute-prefix` and `xml-content-name` flags to identify attributes and content fields.
 
 
-Base64 assumes [rfc4648](https://rfc-editor.org/rfc/rfc4648.html) encoding. Encoding and decoding both assume that the content is a string.
+Base64 assumes [rfc4648](https://rfc-editor.org/rfc/rfc4648.html) encoding. Encoding and decoding both assume that the content is a utf-8 string and not binary content.

pkg/yqlib/doc/operators/headers/load.md

@@ -14,6 +14,8 @@ You can load files of the following supported types:
 | Plain String | load_str |
 | Base64 | load_base64 |
 
+Note that load_base64 only works for base64 encoded utf-8 strings.
+
 ## Samples files for tests:
 
 ### yaml

pkg/yqlib/doc/operators/load.md

@@ -14,6 +14,8 @@ You can load files of the following supported types:
 | Plain String | load_str |
 | Base64 | load_base64 |
 
+Note that load_base64 only works for base64 encoded utf-8 strings.
+
 ## Samples files for tests:
 
 ### yaml