Introduce inline commands : inlineAnchor, inlineCrossReference for easier markup composition

src/main/java/io/github/robwin/markup/builder/AbstractMarkupDocBuilder.java

@@ -109,6 +109,11 @@ public abstract class AbstractMarkupDocBuilder implements MarkupDocBuilder {
         return this;
     }
 
+    @Override
+    public String inlineCrossReference(String anchor) {
+        return inlineCrossReference(anchor, null);
+    }
+
     @Override
     public MarkupDocBuilder newLine(){
         documentBuilder.append(newLine);