earcut worker

[kylebarron]

Change list

• Add build process via esbuild to generate worker
• Change arrow imports to be from the file that exports them, not the top level. I found that this significantly reduced bundle size.

In particular, comparing the tree shaking output of

import { BufferType, Type } from "apache-arrow/enum";
import { Data } from "apache-arrow/data";
import { Vector } from "apache-arrow/vector";
import { Field } from "apache-arrow/schema";

with

import { BufferType, Type } from "apache-arrow";
import { Data } from "apache-arrow";
import { Vector } from "apache-arrow";
import { Field } from "apache-arrow";

Just that one change (from the latter to the former) reduced the minified earcut worker from 205kb to 74kb.

• Remove full data type reconstruction from the earcut worker. Eliminating imports of DataType and Field classes and related functionality reduced bundle size from 74kb to 15kb!!
• Note that all of these bundle sizes are uncompressed!! The brotli-compressed final bundle drops to just 6kb!! 🤯
• I also published 0.3.0-beta.1 from this branch