Enable NON32XFER_HANDLER on ESP8266

This is a platform feature that asks forgiveness for PROGMEM misuse:
it adds a handler such that incorrectly used PROGMEM will work without
crashing, just really, *really* inefficiently.

Given that most of our real-world use cases for PROGMEM strings are
relatively infrequent text calls, we can err on the side of developer
convenience and address performance problems if and when they arise.

platformio.ini

@@ -197,6 +197,7 @@ build_flags =
   ; decrease code cache size and increase IRAM to fit all pixel functions
   -D PIO_FRAMEWORK_ARDUINO_MMU_CACHE16_IRAM48 ;; in case of linker errors like "section `.text1' will not fit in region `iram1_0_seg'"
   ; -D PIO_FRAMEWORK_ARDUINO_MMU_CACHE16_IRAM48_SECHEAP_SHARED ;; (experimental) adds some extra heap, but may cause slowdown
+  -D NON32XFER_HANDLER ;; ask forgiveness for PROGMEM misuse
 
 lib_deps =
   #https://github.com/lorol/LITTLEFS.git