Add movetz and stallent as Swift SDK maintainers (#21)

* Add movetz and stallent as Swift SDK maintainers

Adding Maksym Mova (MacPaw) and Stephen Tallent (Mercury.io) as new
maintainers for the Swift SDK, as discussed in the SDK working group.

* Set up tiered access: admins + contributor team

- movetz and stallent get admin access directly
- swift-sdk team grants push access (for future contributors)

This follows the pattern used by go-sdk and rust-sdk.

* Preserve mattt as admin

src/config/repoAccess.ts

@@ -254,7 +254,12 @@ export const REPOSITORY_ACCESS: RepositoryAccess[] = [
   },
   {
     repository: 'swift-sdk',
-    teams: [{ team: 'swift-sdk', permission: 'admin' }],
+    teams: [{ team: 'swift-sdk', permission: 'push' }],
+    users: [
+      { username: 'mattt', permission: 'admin' },
+      { username: 'movetz', permission: 'admin' },
+      { username: 'stallent', permission: 'admin' },
+    ],
   },
   {
     repository: 'typescript-sdk',