Merge pull request wled#4060 from DedeHai/0_15_bootdelay

boot-up delay to fix wifi not starting in some setups

use
`-D WLED_BOOTUPDELAY=500` (or some other delay you want, in milliseconds)
in platformio env definition to add 500ms of delay before hardware init.

Author: softhack007

wled00/wled.cpp

@@ -343,6 +343,9 @@ void WLED::setup()
   #ifdef ARDUINO_ARCH_ESP32
   pinMode(hardwareRX, INPUT_PULLDOWN); delay(1);        // suppress noise in case RX pin is floating (at low noise energy) - see issue #3128
   #endif
+  #ifdef WLED_BOOTUPDELAY
+  delay(WLED_BOOTUPDELAY); // delay to let voltage stabilize, helps with boot issues on some setups
+  #endif
   Serial.begin(115200);
   #if !ARDUINO_USB_CDC_ON_BOOT
   Serial.setTimeout(50);  // this causes troubles on new MCUs that have a "virtual" USB Serial (HWCDC)