Add trace log primer to the Contributing section

README.md

@@ -78,6 +78,9 @@ Some suggestions to get started:
 
 - You can look at the [good first issue](https://github.com/helix-editor/helix/labels/good%20first%20issue) label on the issue tracker.
 - Help with packaging on various distributions needed!
+- To use print debugging to the `~/.cache/helix/helix.log` file, you must:
+  * Print using `log::info!`, `warn!`, or `error!`. (`log::info!("helix!")`)
+  * Pass the appropriate verbosity level option for the desired log level. (`hx -v <file>` for info, more `v`s for higher severity inclusive)
 - If your preferred language is missing, integrating a tree-sitter grammar for
     it and defining syntax highlight queries for it is straight forward and
     doesn't require much knowledge of the internals.