Update extensions.md to include US Gov (#1140)

Add USG-1 extension reservation @ 990.

---------

Signed-off-by: k2niner <[email protected]>

Author: k2niner

CHANGELOG.md

@@ -104,6 +104,7 @@ Thankyou! -->
 7. Adds support for `suppress_checks` controls in attributes to allow tools to automatically validate conventions #1063
     * Updated several attributes that do not follow conventions to disable linting for them
 8. Added `credential_uid` as an Observable type - type_id: 19. #1137
+9. New Extension registration for US Gov #1140
 
 ## [v1.2.0] - April 23rd, 2024
 

extensions.md

@@ -3,6 +3,7 @@ The purpose of this file is to keep track of and avoid collisions in Extension `
 
 | Caption     | Name     | UID | Notes |
 |-------------|----------|-----|-------|
+| US GOV      | usg1     | **990** | The USG-1 schema extension |
 | Cisco       | cisco    | **991** | The Cisco schema extension |
 | Sedara      | sedara   | **992** | The Sedara schema extension |
 | Sciber      | sciber   | **993** | The Sciber schema extension |