[enhancement] Add a "hold temperature" case

[JLIspace]

Hey, this isn't that important but I'd prefer the temperatur showing:

60.1°C ⇒ 60.0°C
59.8°C ⇒ 60.0°C
instead of
60.1°C ⇘ 60.0°C
59.8°C ⇗ 60.0°C

when the temperatur is approximately the target temperature :)

[Cosik]

@JLIspace what is +/- margin where you want to get this sign?

[JLIspace]

@JLIspace what is +/- margin where you want to get this sign?

I guess around 1° difference should be enough. :)