Add link to modguard show usage docs from overview

docs/index.md

@@ -11,4 +11,4 @@ Modguard is incredibly lightweight, and has no impact on the runtime of your cod
 
 * [`modguard check [dir-name]`](usage.md#modguard) - Check boundaries are respected throughout a directory.
 * [`modguard init [dir-name]`](usage.md#modguard-init) - Initialize package boundaries in a directory.
-* `modguard show [dir-name]` - View and optionally generate a YAML representation of the boundaries in a directory.
+* [`modguard show [dir-name]`](usage.md#modguard-show) - View and optionally generate a YAML representation of the boundaries in a directory.