fix: Library dependency for Platform IO

Author: QuickSander

library.json

@@ -14,6 +14,10 @@
         "type": "git",
         "url": "https://github.com/QuickSander/ArduinoHttpServer.git"
     },
+    "dependencies":
+    {
+      "agdl/Base64": "^1.0.0"
+    }, 
     "frameworks": "arduino",
     "platforms": "*"
 }