Modernize code

[eumiro]

1. Use f-strings
2. Use integers where appropriate
3. Refactor generate_random

[rayrrr]

@eumiro Thank you for this PR! We're currently focusing on getting type annotations PR #203 merged first (FIFO).

Overall, I like what you've done here. However, in the GeoJSON spec in section 3.1.1, it states:

A position is an array of numbers. There MUST be two or more elements. The first two elements are longitude and latitude, or easting and northing, precisely in that order and using decimal numbers.

Emphasis added. The reason you see floats everywhere in the codebase, is because we would like this package to perfectly align with the spec. So, can you please change them back to decimal? From there, a rebase and merge should be all that's needed once we merge in the aforementioned other PR.

[rayrrr]

Upon further review, #203 is not ready for merge, so we can merge this first. I'm merging this and will do a quick follow up PR to change the numbers back to float to match the spec.