Selectable (from menu) partitions for m5stack (#1382)

* Additional partition scheme min_spiffs
with minimal SPIFFS partition size and OTA support for bigger apps

* Selectable (from menu) partitions for m5stack

addition for m5stack (as is prepared for lolin32 board: https://github.com/espressif/arduino-esp32/pull/1379)

discourse here: https://github.com/espressif/arduino-esp32/issues/1378

boards.txt

@@ -1267,6 +1267,15 @@ m5stack-core-esp32.menu.FlashFreq.80.build.flash_freq=80m
 m5stack-core-esp32.menu.FlashFreq.40=40MHz
 m5stack-core-esp32.menu.FlashFreq.40.build.flash_freq=40m
 
+m5stack-core-esp32.menu.PartitionScheme.default=Default
+m5stack-core-esp32.menu.PartitionScheme.default.build.partitions=default
+m5stack-core-esp32.menu.PartitionScheme.no_ota=No OTA (Large APP)
+m5stack-core-esp32.menu.PartitionScheme.no_ota.build.partitions=no_ota
+m5stack-core-esp32.menu.PartitionScheme.no_ota.upload.maximum_size=2097152
+m5stack-core-esp32.menu.PartitionScheme.min_spiffs=Minimal SPIFFS (Large APPS with OTA)
+m5stack-core-esp32.menu.PartitionScheme.min_spiffs.build.partitions=min_spiffs
+m5stack-core-esp32.menu.PartitionScheme.min_spiffs.upload.maximum_size=1966080
+
 m5stack-core-esp32.menu.UploadSpeed.921600=921600
 m5stack-core-esp32.menu.UploadSpeed.921600.upload.speed=921600
 m5stack-core-esp32.menu.UploadSpeed.115200=115200