Change getClassLoader from SmallRyeConfigBuilder to public (#977)

Author: radcortez

implementation/src/main/java/io/smallrye/config/SmallRyeConfigBuilder.java

@@ -585,7 +585,7 @@ public KeyMap<String> getDefaultValues() {
         return defaultValues;
     }
 
-    ClassLoader getClassLoader() {
+    public ClassLoader getClassLoader() {
         return classLoader;
     }