Compile with newer c++ standard

platformio.ini

@@ -20,6 +20,10 @@ platform = espressif32@>=6.0.1
 build_flags =
     -DCOMPONENT_EMBED_FILES=webapp_dist/index.html.gz:webapp_dist/zones.json.gz:webapp_dist/favicon.ico:webapp_dist/js/app.js.gz
     -Wall -Wextra -Werror
+    -std=c++17
+    -std=gnu++17
+build_unflags =
+    -std=gnu++11
 
 lib_deps =
     https://github.com/yubox-node-org/ESPAsyncWebServer