Add Zach Steindler as co-chair

Signed-off-by: Zach Steindler <[email protected]>

Author: steiza

README.md

@@ -36,7 +36,7 @@ We use the [securing-software-repos-wg](https://github.com/orgs/ossf/teams/secur
 
 The [CHARTER.md](https://github.com/ossf/wg-securing-software-repos/blob/main/CHARTER.md) outlines the scope and governance of our group activities.
 
-This group is chaired by [Dustin Ingram](https://github.com/di).
+This group is co-chaired by [Dustin Ingram](https://github.com/di) and [Zach Steindler](https://github.com/steiza).
 
 ## Communication