Configure nohttp to ignore docs build output

At present, project build fails with checkstyleNohttp task error if not cleaned beforehand.

This commit updates nohttp configuration so that it ignores build output of examples in spring-session-docs module.

Closes gh-2127

Author: vpavic

build.gradle

@@ -45,4 +45,6 @@ subprojects {
 
 nohttp {
     source.exclude "buildSrc/build/**"
+	source.exclude "spring-session-docs/.gradle/nodejs/**"
+	source.exclude "spring-session-docs/modules/ROOT/examples/**/build/**"
 }