Add icons to admonitions

[HarshKapadia2]

• Read up on admonitions from the AsciiDoc Syntax Reference.
• The problem is that these icons are rendered in .adoc (Asciidoctor) files, but not in the rendered HTML file that is hosted.
  Eg:

.adoc file:

Rendered HTML file:

• See if the icons can be rendered.
• If not, a workaround could be to include the image files in ./src/images and then insert them using a style tag in the head of a Docinfo file.

[HarshKapadia2]

Thank you SO much, @KartikSoneji!