phpDocumentor: update the configuration to v 3

* Update the configuration to the format used by phpDocumentor 3.
    Ref: https://docs.phpdoc.org/3.0/references/configuration.html
* Rename the file from `phpdoc.xml.dist` to `phpdoc.dist.xml`.
    Turns out this project uses the reverse extension order compared to, for instance, PHPUnit and PHPCS.
    If no issue is open about this in phpDocumentor, I will open one in the near future.

Author: jrfnl

phpdoc.dist.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<phpdocumentor
+    configVersion="3"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://www.phpdoc.org"
+    xsi:noNamespaceSchemaLocation="https://docs.phpdoc.org/latest/phpdoc.xsd"
+>
+
+    <title>PHPCSUtils</title>
+
+    <paths>
+        <output>docs/phpdoc/</output>
+        <cache>build/docs/structure/</cache>
+    </paths>
+
+    <version number="latest">
+        <api format="php">
+            <source dsn=".">
+                <path>phpcsutils-autoload.php</path>
+                <path>PHPCSUtils</path>
+            </source>
+        </api>
+    </version>
+
+    <template name="default"/>
+
+</phpdocumentor>