docs/dasharo-tools-suite/documentation/features.md: add btg key validator

Signed-off-by: Michał Kopeć <[email protected]>

Author: mkopec

docs/dasharo-tools-suite/documentation/features.md

@@ -552,3 +552,15 @@ v1.2.20, pending the resolution of this issue. We will reintroduce them once we
 determine the appropriate action to address this dependency. Progress on this
 matter is being monitored through issue
 [288](https://github.com/Dasharo/dasharo-issues/issues/288).
+
+### Verify Boot Guard key
+
+It's possible to verify if the currently running firmware is signed using the
+correct Boot Guard key for the given platform. To do this:
+
+1. Enter the shell in DTS
+
+1. Execute `btg_key_validator`
+
+The script will output information whether the platform firmware is signed with
+the correct Boot Guard key.