Add the ability to use line icons for the forecast

[ibocharov]

Is your feature request related to a problem? Please describe.
Each update I need to update it manually on my side, so could you please add the ability to use line icons for the forecast via configuration

Describe the solution you'd like
Get icon type from configuration instead of hardcoded 'fill' value @ #L210

Additional context
Additionally, on a light background there icons are almost unreadable :(

So as a workaround, I've added card_mod style for icons

forecast-icon {
    filter: brightness(75%) contrast(125%) saturate(2000%);
}

[curtisbarnard]

Just wanted to add on that I'd love to have this feature as well. Allow users to use line icons and also specify the colors for each icon. In the meantime @ibocharov can you give a run down on what you've changed to make the switch on your instance?