Add check for SPIFFS name lenght
Add check for SPIFFS name lenght

- Checks if file name len in SPIFFS is lower than 30,
  as this is SPIFFS limit

Signed-off-by: Martin Mihálek <50acdaf2f3fddad14028ba2cdf8c01f875c851bb@gmail.com>

aenniw/ESP8266,aenniw/ESP8266,aenniw/ESP8266