Update capabilities to be expressible by Boolean literals (#16)

* Conform Server.Capabilities types to ExpressibleByBooleanLiteral

* Conform Client.Capabilities types to ExpressibleByBooleanLiteral

* Use Boolean literatls for capabilities in tests

* Update README

Tests/MCPTests/RoundtripTests.swift

@@ -34,9 +34,9 @@ struct RoundtripTests {
             name: "TestServer",
             version: "1.0.0",
             capabilities: .init(
-                prompts: .init(),
-                resources: .init(),
-                tools: .init()
+                prompts: true,
+                resources: true,
+                tools: true
             )
         )
         await server.withMethodHandler(ListTools.self) { _ in