pio: notice about macOS big sur

code/platformio.ini

@@ -38,6 +38,10 @@ extra_configs =
 #
 # ------------------------------------------------------------------------------
 
+# TODO(espressif8266@2.6.2): https://github.com/xoseperez/espurna/wiki/PlatformIO#macos-big-sur
+# Current version needs `platformio/tool-esptoolpy @ ~1.30000.0`
+# (or, just avoiding `-t upload` and using esptool script manually)
+
 platform = espressif8266@2.6.2
 platform_latest = espressif8266@2.6.2