docs(shippy): update README with config option explanations

shippy/README.md

@@ -1,4 +1,5 @@
 # shippy
+
 [
 ![PyPI](https://img.shields.io/pypi/v/shipper-shippy)
 ![PyPI - Downloads](https://img.shields.io/pypi/dm/shipper-shippy)
@@ -32,20 +33,30 @@ server = https://example.com
 token = a1b2c3d4e5...
 DisableBuildOnUpload = false
 UploadWithoutPrompt = false
+debug = false
 ```
 
 Configuration options explained:
 
 ### `server`
+
 Server URL
 
 ### `token`
+
 Token used to sign in to the server
 
 ### `DisableBuildOnUpload`
+
 Immediately disables the build after uploading it. Useful if you are uploading from Jenkins or uploading potentially
 unstable builds. Do NOT use under normal circumstances!
 
 ### `UploadWithoutPrompt`
+
 shippy will not prompt you before uploading builds, and will automatically upload all builds found in the current
 directory. Use with caution. Same as the `-y`/`--yes` flag shown above.
+
+### `debug`
+
+Enable debug mode for all invocations. When set to true, the `-d`/`--debug` flag will have no effect, and all
+invocations of shippy will run with debug mode enabled.