Adopt type=module

[Fil]

follow changes in d3-format:

• type=module
• add exports
• remove zip
• license: ISC
• update dependencies

TODO:

• [x] update README.md
• [x] check LICENSE
• [x] check CLI
• [x] compare-image and compute-scale
• [x] depends on d3-geo@3
• [x] switch the default branch to main

[mbostock]

I rewrote the d3-geo snapshot tests to use pixelmatch, and it seems to work well:

https://github.com/d3/d3-geo/commit/356d26f62760be5cc908334dd858faead87fa4db

Do you want to take a crack at updating this PR to match? (And adding the .github/eslint.json, updating the rollup.config.js to extract the copyright from the LICENSE, upgrading the dependencies, using named imports in the tests, etc.)

The biggest question in my mind right now is how the CLI will work in a pure ES modules environment, given that geoproject currently takes a -r argument to require a library (e.g., d3-geo-polygon). I think we can just use dynamic import (e.g., import("d3-geo-polygon"))… but I haven’t tested that approach yet.