docs: Update iac.md to cover --depth-detection

Author: aron

help/commands-docs/iac-examples.md

@@ -7,3 +7,6 @@
 
 - `Test terraform file`:
   \$ snyk iac test /path/to/terraform_file.tf
+
+- `Test matching files in a directory`:
+  \$ snyk iac test /path/to/directory

help/commands-docs/iac.md

@@ -17,6 +17,14 @@ Find security issues in your Infrastructure as Code files.
 
 ## OPTIONS
 
+- `--detection-depth`=<DEPTH>:
+  (only in `test` command)  
+  Indicate the maximum depth of sub-directories to search. <DEPTH> must be a number.
+
+  Default: No Limit  
+  Example: `--detection-depth=3`  
+  Will limit search to provided directory (or current directory if no <PATH> provided) plus two levels of subdirectories.
+
 - `--severity-threshold`=low|medium|high:
   Only report vulnerabilities of provided level or higher.