docs: add troubleshooting guide

First troubleshooting entry documents error message seen when missing
read permission on the trash executable.

Fixes #14

README.md

@@ -105,6 +105,7 @@ provided below for some main topics.
 
 - [Command Line Reference](../../wiki/Command-Line-Reference)
 - [Configuration Reference](../../wiki/Configuration-Reference)
+- [Troubleshooting](../../wiki/Troubleshooting)
 
 ## Important Notices
 

wiki/Troubleshooting.md

@@ -0,0 +1,14 @@
+# Errors & Solutions
+
+* On Mac or Linux OS, you may see the following error when you run `trash`:
+
+  ```txt
+  Failed to map file. open(/Users/foo/Downloads/trash) failed with error 13
+  Failure processing application bundle.
+  Couldn't memory map the bundle file for reading.
+  A fatal error occured while processing application bundle
+  ```
+
+  This cryptic message is actually a permissions error, likely because your executable does not have
+  read permissions set. Simply run `chmod u+rx trash` to add read + execute permissions on the
+  `trash` executable. This is also done in the linux one-liner outlined in the main `README.md`.