feat: add updater signing public key

Author: afonsojramos

src-tauri/tauri.conf.json

@@ -73,7 +73,8 @@
     "updater": {
       "endpoints": [
         "https://github.com/gitify-app/gitify/releases/latest/download/latest.json"
-      ]
+      ],
+      "pubkey": "dW50cnVzdGVkIGNvbW1lbnQ6IG1pbmlzaWduIHB1YmxpYyBrZXk6IEIxQTRFMUU0OTQ2MUZCOUEKUldTYSsyR1U1T0drc2UyTFpFaEQwOUoyaXhZQlpmUURhK1F3U2xtYzNHbENWcEwyT3JXWkYwZDAK"
     },
     "deep-link": {
       "desktop": {