Documentation: primer: AsciiDoc link macro

Begin making proper use of the macro.

Prefixing: 

- only where necessary
- not with https: or mailto: URL schemes.

documentation/content/en/books/fdp-primer/asciidoctor-primer/_index.adoc

@@ -49,8 +49,8 @@ endif::[]
 
 Most FDP documentation is written with AsciiDoc.
 This chapter explains what that means, how to read and understand the documentation source, and the techniques used.
-To get a complete reference of the AsciiDoctor capabilities please consult the link:https://docs.asciidoctor.org/home/[Asciidoctor documentation].
-Some of the examples used in this chapter have been taken from the link:https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference[AsciiDoc Syntax Quick Reference].
+To get a complete reference of the AsciiDoctor capabilities please consult the https://docs.asciidoctor.org/home/[Asciidoctor documentation].
+Some of the examples used in this chapter have been taken from the https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference[AsciiDoc Syntax Quick Reference].
 
 [[asciidoctor-primer-overview]]
 == Overview
@@ -156,7 +156,7 @@ And this is the second paragraph.
 == Lists
 
 AsciiDoctor supports a few types of lists, the most common are `ordered` and `unordered`.
-To get more information about lists, see link:https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/#lists[AsciiDoc Syntax Quick Reference].
+To get more information about lists, see https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/#lists[AsciiDoc Syntax Quick Reference].
 
 [[asciidoctor-ordered-lists]]
 === Ordered lists
@@ -206,17 +206,9 @@ And this would be rendered as.
 [[asciidoctor-links-external]]
 === External links
 
-To point to another website the `link` macro should be used.
+The `link:` macro prefix is https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/#links[*not* required] when the target starts with a URL scheme such as `https:` or `mailto:`. 
 
-....
-link:https://www.FreeBSD.org[FreeBSD]
-....
-
-[NOTE]
-====
-As the AsciiDoctor documentation describes, the `link` macro is not required when the target starts with a URL scheme like `https`.
-However, it is a good practice to do this anyway to ensure that AsciiDoctor renders the link correctly, especially in non-latin languages like Japanese.
-====
+The URL scheme acts as an implicit macro prefix. 
 
 [[asciidoctor-links-internal]]
 === Internal link
@@ -240,6 +232,11 @@ And this would be rendered as.
 +
 extref:{ipsec-must}[IPSec-Must article]
 
+[[asciidoctor-link-macro]]
+=== The link macro
+
+This macro is not often needed. Use cases are https://docs.asciidoctor.org/asciidoc/latest/macros/link-macro/#when-to-use-the-link-macro[specified in Asciidoctor Docs].
+
 [[asciidoctor-conclusion]]
 == Conclusion