Merge pull request #287 from draco2003/patch-1

@draco2003 Your PR is not a small fix. It helps my lacking ability.
Thank you for your PR.

examples/mqttRSSI/mqttRSSI.ino

@@ -2,7 +2,7 @@
 ESP8266/ESP32 publish the RSSI as the WiFi signal strength to ThingSpeak channel.
 This example is for explaining how to use the AutoConnect library.
 
-In order to execute this example, the ThingSpeak account is needed. Sing up
+In order to execute this example, the ThingSpeak account is needed. Sign up
 for New User Account and create a New Channel via My Channels.
 For details, please refer to the project page.
 https://hieromon.github.io/AutoConnect/howtoembed.html#used-with-mqtt-as-a-client-application