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/users.ts

@@ -232,6 +232,10 @@ export const MEMBERS: readonly Member[] = [
     github: 'michaelneale',
     memberOf: ['rust-sdk'],
   },
+  {
+    github: 'movetz',
+    memberOf: ['swift-sdk'],
+  },
   {
     github: 'mikekistler',
     memberOf: ['csharp-sdk'],
@@ -304,6 +308,10 @@ export const MEMBERS: readonly Member[] = [
     github: 'stephentoub',
     memberOf: ['csharp-sdk'],
   },
+  {
+    github: 'stallent',
+    memberOf: ['swift-sdk'],
+  },
   {
     github: 'tadasant',
     email: 'tadas@modelcontextprotocol.io',