include the properties files examples instead of linking to the example file in master

Author: jimczi

docs/plugins/authors.asciidoc

@@ -1,6 +1,8 @@
 [[plugin-authors]]
 == Help for plugin authors
 
+:plugin-properties-files: {docdir}/../../buildSrc/src/main/resources
+
 The Elasticsearch repository contains examples of:
 
 * a https://github.com/elastic/elasticsearch/tree/master/plugins/jvm-example[Java plugin]
@@ -24,10 +26,13 @@ All plugin files must be contained in a directory called `elasticsearch`.
 [float]
 === Plugin descriptor file
 
-All plugins must contain a file called `plugin-descriptor.properties` in the folder named `elasticsearch`. The format
-for this file is described in detail here:
+All plugins must contain a file called `plugin-descriptor.properties` in the folder named `elasticsearch`.
+The format for this file is described in detail in this example:
 
-https://github.com/elastic/elasticsearch/blob/master/buildSrc/src/main/resources/plugin-descriptor.properties[`/buildSrc/src/main/resources/plugin-descriptor.properties`].
+["source","properties",subs="attributes"]
+--------------------------------------------------
+include-tagged::{plugin-properties-files}/plugin-descriptor.properties[plugin-descriptor.properties]
+--------------------------------------------------
 
 Either fill in this template yourself or, if you are using Elasticsearch's Gradle build system, you
 can fill in the necessary values in the `build.gradle` file for your plugin.
@@ -125,8 +130,12 @@ for more information.
 It is also possible to bundle multiple plugins into a meta plugin.
 A directory for each sub-plugin must be contained in a directory called `elasticsearch.
 The meta plugin must also contain a file called `meta-plugin-descriptor.properties` in the directory named
-`elasticsearch`. The format for this file is described in detail here:
+`elasticsearch`.
+The format for this file is described in detail in this example:
 
-https://github.com/elastic/elasticsearch/blob/master/buildSrc/src/main/resources/plugin-descriptor.properties[`/buildSrc/src/main/resources/meta-plugin-descriptor.properties`].
+["source","properties",subs="attributes"]
+--------------------------------------------------
+include-tagged::{plugin-properties-files}/meta-plugin-descriptor.properties[meta-plugin-descriptor.properties]
+--------------------------------------------------
 
 A meta plugin can be installed/removed like a normal plugin with the `bin/elasticsearch-plugin` command.