Add config files to the CLI reference page (#688)

The CLI reference or man page for precli contains a list of files that
precli will work with. This change adds files that precli will attempt
to read for configuration information. Namely, .precli.toml,
precli.toml, and pyproject.toml.

Signed-off-by: Eric Brown <eric.brown@securesauce.dev>

docs/man/precli.md

@@ -36,10 +36,22 @@ certificate validation, and more.
 
 ## FILES
 
-.preignore
+`.preignore`
 
   file that specifies which files and directories can be ignored
 
+`.precli.toml`
+
+  file that specifies custom configuration
+
+`precli.toml`
+
+  same as `.precli.toml`
+
+`pyproject.toml`
+
+  standard Python configuration file where precli can read configuration
+
 ## ENVIRONMENT VARIABLES
 
 DEBUG