Add zeroconf discovery to homekit (#39907)

Ensures HomeKit Bridge is offered for onboarding if
homekit is detected on the network.

homeassistant/components/homekit/manifest.json

@@ -20,5 +20,6 @@
   "codeowners": [
     "@bdraco"
   ],
+  "zeroconf": ["_homekit._tcp.local."],
   "config_flow": true
 }

homeassistant/generated/zeroconf.py

@@ -37,6 +37,9 @@ ZEROCONF = {
     "_hap._tcp.local.": [
         "homekit_controller"
     ],
+    "_homekit._tcp.local.": [
+        "homekit"
+    ],
     "_http._tcp.local.": [
         "shelly"
     ],