Fix comment syntax in prepend.csv

[yecril23pl]

Fix casing, embedded path syntax and embedded shell command syntax in the introduction to the file prepend.csv

[johnraff]

@yecril23pl thank you for your suggestions. These are all questions of style rather than errors, and do not justify editing in my opinion. On the BL forum, code snippets are often indicated by surrounding them with single quotes. Since we are talking about comments rather than executed code there is no need to enforce any particular syntax. Thanks again!