docs: add @ckerr to Upgrades WG (#397)

wg-upgrades/README.md

@@ -11,6 +11,7 @@ Oversees upgrades of upstream dependencies; specifically Chromium and Node.
 | <img src="https://github.com/nornagon.png" width=100 alt="@nornagon">  | Jeremy Rose [@nornagon](https://github.com/nornagon) | Member | PT (San Francisco) |
 | <img src="https://github.com/marshallofsound.png" width=100 alt="@marshallofsound">  | Samuel Attard [@MarshallOfSound](https://github.com/marshallofsound) | Member | PT (Vancouver) |
 | <img src="https://github.com/jkleinsc.png" width=100 alt="@nornagon">  | John Kleinschmidt [@jkleinsc](https://github.com/jkleinsc) | Member | ET (Harrisburg) |
+| <img src="https://github.com/ckerr.png" width=100 alt="@ckerr">  | Charles Kerr [@ckerr](https://github.com/ckerr) | Member | CT (New Orleans) |
 
 ## Areas of Responsibility