code: public MarkdownTagletExecutor register(MarkdownTaglet markdownTaglet) {
          final MarkdownTaglet old = tags.put(markdownTaglet.getName(), markdownTaglet);
          if (old != null) {
              errorHandler.overrideMarkdownTaglet(old, markdownTaglet);
          }
  
          return this;
      }
docs: Register an {@link MarkdownTaglet}.
  <p>
  **Caution**: If already an InlineTag with the same {@linkplain MarkdownTaglet#getName() name} exists, then
  <p>
  + {@link MarkdownTagletErrorHandler#overrideMarkdownTaglet(MarkdownTaglet, MarkdownTaglet)} will be called
  + the existing will be replaced by the new one.
  
  @param markdownTaglet the {@code InlineTag}
  @return self