Update help file re Save Snippet Information dialogue box changes

[delphidabbler]

Once finished adding new output options to the Save Snippet Information dialogue box, the help file needs to be updated.

Finish the following issues first:

• Add option to save snippet information in plain text #162
• Add option to save snippet information in HTML #153
• Add option to save snippet information in Markdown format #155

Tick these off once pushed to develop