Add Anders Bertelrud and Daniel Dunbar as additional code owners for SwiftPM.

Author: rballard

CODE_OWNERS.txt

@@ -8,6 +8,14 @@ beautification by scripts.  The fields are: name (N), email (E), web-address
 (W), PGP key ID and fingerprint (P), description (D), and snail-mail address
 (S).
 
+N: Anders Bertelrud
+E: [email protected]
+D: Package Manager
+
+N: Daniel Dunbar
+E: [email protected]
+D: Package Manager
+
 N: Max Howell
 E: [email protected]
 D: Package Manager