feat: optionalTagName for javadocs in jdt

[pouryafard75]

This is the fix for #355

@author john */ class C {} now will be represented as:

CompilationUnit [0,30]
                TypeDeclaration [0,30]
                    Javadoc [0,19]
                        TagElement [4,17]
                            TAG_NAME: @author [4,11]
                            TextElement:  john  [11,17]
                    TYPE_DECLARATION_KIND: class [20,25]
                    SimpleName: C [26,27]