Adding a manpage built from README.md

Just a simple man page I wrote in (hopeful) anticipation of adding **salsapipe** to [Arch Assault](https://archassault.org). Feel free to add it regardless of your decision on licensing.

In case the license you go with requires this for you to continue having full creative control: I, Kevin MacMartin (the author of this commit), hereby grant full copyright surrounding the changes made in this commit to **0xcaca0** (the original author of this project).

Cheers!