Create fix-macos-certificates.md

Create changefile for the fixes.

Signed-off-by: Ayush Singh <ayush@beagleboard.org>

Author: Ayush1325

.changes/fix-macos-certificates.md

@@ -0,0 +1,6 @@
+---
+"cargo-packager": patch
+"@crabnebula/packager": patch
+---
+
+Fix bug that prevents reading macos signing certificates from environment variables.