Update PlatformIO Core versions (#1734)

* Added new core versions 2.5.1/2.5.2 with matching PlatformIO versions

* Update platformio.ini

code/platformio.ini

@@ -14,12 +14,16 @@ data_dir = espurna/data
 #   arduino core 2.4.1 = platformIO 1.7.3
 #   arduino core 2.4.2 = platformIO 1.8.0
 #   arduino core 2.5.0 = platformIO 2.0.4
+#   arduino core 2.5.1 = platformIO 2.1.1
+#   arduino core 2.5.2 = platformIO 2.2.1
 # ------------------------------------------------------------------------------
 arduino_core_2_3_0 = espressif8266@1.5.0
 arduino_core_2_4_0 = espressif8266@1.6.0
 arduino_core_2_4_1 = espressif8266@1.7.3
 arduino_core_2_4_2 = espressif8266@1.8.0
 arduino_core_2_5_0 = espressif8266@2.0.4
+arduino_core_2_5_1 = espressif8266@2.1.1
+arduino_core_2_5_2 = espressif8266@2.2.1
 
 platform = ${common.arduino_core_2_3_0}
 platform_latest = ${common.arduino_core_2_4_2}