Fix decimal and checksum

[ruisilvalink]

My sensor is reporting decimal temperature values.
Because of that, the checksum wasn't working.

[MikeNatsu]

This fixed my issue with checksum error, why isn't this merge yet?

[k3ldar]

Just checked this fix locally and it seems the decimal goes up in weird increments:

22.01
22.02
...
22.09
22.1

Changing lines 79/80 to * 0.1 fixed it for me so it seems more accurate to 1 decimal place.

For what it's worth but nice mod :-)