Add getConnectionCount function

src/WebSerial.cpp

@@ -114,6 +114,10 @@ void WebSerialClass::onMessage(WSLStringMessageHandler callback) {
   };
 }
 
+bool WebSerialClass::getConnectionCount() {
+  return _ws->count();
+}
+
 // Print func
 size_t WebSerialClass::write(uint8_t m) {
   if (!_ws)

src/WebSerial.h

@@ -97,6 +97,7 @@ class WebSerialClass : public Print {
     void setAuthentication(const String& username, const String& password);
     void onMessage(WSLMessageHandler recv);
     void onMessage(WSLStringMessageHandler recv);
+    bool getConnectionCount();
     size_t write(uint8_t) override;
     size_t write(const uint8_t* buffer, size_t size) override;