Add support for SWEREF 99 TM datum

Hi,

I'm using the InReach Mini in Sweden. It would be nice to be able to display coordinates in the SWEREF 99 TM datum, as that is what we have printed on most maps. The device comes with RT 90, but that isn't used since more than a decade. Other Garmin devices, such as my Fenix 6x is able to display coordinates this way. 

More information regarding SWEREF 99 TM: https://epsg.io/3006

/Edvard