Add phpmd with ruleset

Author: dan-on

composer.json

@@ -24,6 +24,7 @@
         "phpstan/phpstan": "^0.12.91",
         "vimeo/psalm": "^4.8",
         "phpbench/phpbench": "^1.0",
-        "squizlabs/php_codesniffer": "^3.6"
+        "squizlabs/php_codesniffer": "^3.6",
+        "phpmd/phpmd": "^2.10"
     }
 }

phpmd.ruleset.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ruleset name="php-interval-tree-ruleset"
+         xmlns="http://pmd.sf.net/ruleset/1.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://pmd.sf.net/ruleset/1.0.0 http://pmd.sf.net/ruleset_xml_schema.xsd"
+         xsi:noNamespaceSchemaLocation="http://pmd.sf.net/ruleset_xml_schema.xsd">
+    <description>PHP Interval Tree ruleset</description>
+    <rule ref="rulesets/controversial.xml/CamelCaseClassName"/>
+    <rule ref="rulesets/controversial.xml/CamelCasePropertyName"/>
+    <rule ref="rulesets/controversial.xml/CamelCaseMethodName"/>
+    <rule ref="rulesets/controversial.xml/CamelCaseParameterName"/>
+    <rule ref="rulesets/controversial.xml/CamelCaseVariableName"/>
+    <rule ref="rulesets/design.xml"/>
+    <rule ref="rulesets/unusedcode.xml"/>
+</ruleset>