Add pre post message example for scaffold readme (#232)

Author: ernilambar

README.md

@@ -252,6 +252,20 @@ In this example:
 * "support" -> "body" uses a remote Markdown file as the section contents. This can also be a local file path, or a string.
 * "show_powered_by" shows or hides the Powered By mention at the end of the readme.
 
+For sections, "pre", "body" and "post" are supported. Example:
+```
+"support": {
+  "pre": "highlight.md",
+  "body": "https://raw.githubusercontent.com/runcommand/runcommand-theme/master/bin/readme-partials/support-open-source.md",
+  "post": "This is additional text to show after main body content."
+},
+```
+In this example:
+
+* "pre" content is pulled from local highlight.md file.
+* "body" content is pulled from remote URL.
+* "post" is a string.
+
 **OPTIONS**
 
 	<dir>

src/ScaffoldPackageCommand.php

@@ -208,6 +208,20 @@ public function package( $args, $assoc_args ) {
 	 * * "support" -> "body" uses a remote Markdown file as the section contents. This can also be a local file path, or a string.
 	 * * "show_powered_by" shows or hides the Powered By mention at the end of the readme.
 	 *
+	 * For sections, "pre", "body" and "post" are supported. Example:
+	 * ```
+	 * "support": {
+	 *   "pre": "highlight.md",
+	 *   "body": "https://raw.githubusercontent.com/runcommand/runcommand-theme/master/bin/readme-partials/support-open-source.md",
+	 *   "post": "This is additional text to show after main body content."
+	 * },
+	 * ```
+	 * In this example:
+	 *
+	 * * "pre" content is pulled from local highlight.md file.
+	 * * "body" content is pulled from remote URL.
+	 * * "post" is a string.
+	 *
 	 * ## OPTIONS
 	 *
 	 * <dir>