Add option to save snippet information in Markdown format

[delphidabbler]

An obvious option is to save the snippet information as Markdown.

We would need a Markdown highlighter which would be quite simple:

1. If highlighting was not required the output would be unhighlighted source code surrounded by code fences:

    ```
    unhighlighted-source-code
    ```
   

2. If highlighting was to be supported the opening code fence would need to be followed by pascal:

    ```pascal
    unhighlighted-source-code
    ```