code compatibility readme with write functions

[SergeiSOficial]

In code we have:

typedef BME280_INTF_RET_TYPE (*bme280_write_fptr_t)(uint8_t reg_addr, const uint8_t *reg_data, uint32_t len,
                                                    void *intf_ptr);

but in readme we need change:

int8_t user_spi_write(uint8_t reg_addr, uint8_t *reg_data, uint32_t len, void *intf_ptr)
int8_t user_i2c_write(uint8_t reg_addr, uint8_t *reg_data, uint32_t len, void *intf_ptr)

to this:

int8_t user_spi_write(uint8_t reg_addr, const uint8_t *reg_data, uint32_t len, void *intf_ptr)
int8_t user_i2c_write(uint8_t reg_addr, const uint8_t *reg_data, uint32_t len, void *intf_ptr)