Edit convert functions to output linear interpolation

[Jo-IE]

This PR closes #6840. I edited the convertPropertyFunction and the convertZoomFunction to output linear interpolations when base is 1.

I also ran yarn lint --fix locally to fix linting errors. I am also getting some JSDocs warnings after running yarn lint --fix.

[arindam1993]

Hey @Jo-IE 👋 , thanks a lot for your contribution! Much appreciated!

I think your logic is good overall, but could you please make your change without having run yarn lint --fix? The extra diffs are making the change hard to understand with the extra new-lines.

I'd recommend running yarn run lint only and fixing only the errors manually.

[Jo-IE]

Thank you @arindam1993! I will make those adjustments