Add flakes attribute to use in testsuite report (#3306) (#3308)

Co-authored-by: Piotrek Żygieło <11896137+pzygielo@users.noreply.github.com>
Co-authored-by: Piotrek Żygieło <pzygielo@users.noreply.github.com>

Author: olamy

maven-surefire-plugin/src/site/resources/xsd/surefire-test-report.xsd

@@ -128,6 +128,7 @@
       <xs:attribute name="errors" type="xs:string" use="required"/>
       <xs:attribute name="skipped" type="xs:string" use="required"/>
       <xs:attribute name="failures" type="xs:string" use="required"/>
+      <xs:attribute name="flakes" type="xs:string"/>
       <xs:attribute name="group" type="xs:string"/>
     </xs:complexType>
   </xs:element>