Software serial: compress edge detection buffer as soon as possible

Otherwise we're risking a bit of data loss occassionally.

Author: dirkmueller

airrohr-firmware/Versions.md

@@ -1,5 +1,6 @@
 NRZ-2019-126-B6
 * Read SDS011 version once on startup
+* Put software serial edge detection work within loop
 
 NRZ-2019-126-B5
 * Rename Luftdaten.info to Sensors.Community everywhere

airrohr-firmware/airrohr-firmware.ino

@@ -4486,6 +4486,7 @@ void loop(void) {
 	yield();
 #if defined(ESP8266)
 	MDNS.update();
+	serialSDS.perform_work();
 #endif
 
 	if (sample_count % 500 == 0) {