Expand P2GT menu readme

Author: artlbv

L1Trigger/Configuration/python/Phase2GTMenus/README.md

@@ -12,3 +12,14 @@ Available menus:
 * `step1_2024` -> the 2024 version 
 * `step1_2024_explicitSeeds` –> the 2024 version with explicit definitions of individual objects
 
+These menus can be specified via the cmsDriver configuration as `-s L1P2GT:step1_2024`.
+
+Note that the full menu expanded configuration can be inspected using `edmConfigDump` on a `cmsRun` config that executes the `L1P2GT` step:
+1. Produce the config via 
+```
+cmsDriver.py -s L1P2GT --conditions auto:phase2_realistic_T33 --filein file:file.root --no_exec --python_filename l1pgt_cfg.py
+```
+2. Dump the config via 
+```
+edmConfigDump l1pgt_cfg.py > edm_l1pgt_cfg.py
+```