[enhancement] Add "." (dot) symbol to radio display

[CyberGuerro]

When Selector is setted to COM1, COM2, NAV1, NAV2 it would be useful to see on display value like "134.90" instead of "13490"

I think that it could be possible introducing a parameter in line statement
from
line="on_select:SW_UP_COM1,dataref:sim/cockpit/radios/com1_freq_hz"
to
line="on_select:SW_UP_COM1,dataref:sim/cockpit/radios/com1_freq_hz,dot_position:3"
where "dot_position" is the key and "3" is the digit after which is positioned the "." symbol.

[norberttak]

I added the dot_position option. Here it is a test build for Linux: https://github.com/norberttak/XPanel/actions/runs/8910295579/artifacts/1463916654

See some details in PR #106

[CyberGuerro]

Perfect, updated my xpanel.ini files, tested and all works like expected.
Great job