add icons for nwc and labels plugins

electrum/plugins/labels/manifest.json

@@ -2,5 +2,6 @@
   "name": "labels",
   "fullname": "LabelSync",
   "description": "Save your wallet labels on a remote server, and synchronize them across multiple devices where you use Electrum. Labels, transactions IDs and addresses are encrypted before they are sent to the remote server.",
+  "icon":"labelsync.png",
   "available_for": ["qt", "qml", "cmdline"]
 }

electrum/plugins/nwc/manifest.json

@@ -4,5 +4,6 @@
   "description": "This plugin allows remote control of Electrum lightning wallets via Nostr NIP-47.",
   "author": "The Electrum Developers",
   "available_for": ["cmdline", "qt"],
+  "icon":"nwc.png",
   "version": "0.0.1"
 }