[git] Ignore profiler directory and define how to use in extension

Author: hazendaz

.gitignore

@@ -10,6 +10,7 @@
 /release.properties
 /target
 .github/keys/
+.profiler/
 
 # These are needed if running in IDE without properties set
 /ibderby

.mvn/extensions.xml

@@ -17,6 +17,7 @@
 
 -->
 <extensions>
+    <!-- Usage as -Dprofile -->
     <extension>
       <groupId>fr.jcgay.maven</groupId>
       <artifactId>maven-profiler</artifactId>