fix: add missing service capabilities (#2911)

This is used to know when a service as the pub sub capabilities

Signed-off-by: Sacha Froment <sfroment42@gmail.com>

Author: sfroment

packages/pubsub-floodsub/src/index.ts

@@ -32,7 +32,7 @@
  * ```
  */
 
-import { pubSubSymbol, serviceDependencies } from '@libp2p/interface'
+import { pubSubSymbol, serviceCapabilities, serviceDependencies } from '@libp2p/interface'
 import { PubSubBaseProtocol, type PubSubComponents } from '@libp2p/pubsub'
 import { toString } from 'uint8arrays/to-string'
 import { SimpleTimeCache } from './cache.js'
@@ -82,6 +82,10 @@ class FloodSub extends PubSubBaseProtocol {
 
   readonly [Symbol.toStringTag] = '@libp2p/floodsub'
 
+  readonly [serviceCapabilities]: string[] = [
+    '@libp2p/pubsub'
+  ]
+
   readonly [serviceDependencies]: string[] = [
     '@libp2p/identify'
   ]