feat!: remove CommonJS support

[broofa]

PR showing what happens if we drop CommonJS support.

Briefly:

• Update README verbiage. (Note: fixes minor bug in runmd setup, causing UUIDs to change)
• Switch examples/browser-rollup config from CJS -> ESM
• Drop CJS test from examples/browser-webpack
• Drop examples/node-commonjs
• Switch examples/node-jest from CJS -> ESM. (Requires upgrading to jest@30)
• Remove CJS logic from build.sh
  • Also change from four dist subdirs - "dist/[ esm | esm-browser | cjs | cjs-browser ]" - to just "dist" and "dist-browser"
• (cleanup) Only bundle one set of TS types (in the "dist" dir)
  • types field to explicitly point to "dist/index.d.ts"
• Simplify package.json fields (fwiw, this is motivated by how @sindresorhus appears to be structuring package.json for his 100's of popular ESM-only packages.)
  • Remove main field (only used for CJS entry points)
  • Remove module field (it was never a standard and has been replaced by "exports")
  • In exports, remove import and require instead specify default (esm) and browser (esm-browser)
• Replace the 4 tsconfig.* files we'd been using to handle the multiple TS configs for ESM & CJS with a single tsconfig.json file for the ESM config.

The net effect of the above:

• Source files deleted: 8
• Source lines of code deleted: 271
• Installed package file size: 788K -> 312K
• Installed package file count: 197 -> 77

Closes #881

[LinusU]

Nice cleanup 🤩

[43081j]

@broofa is there a plan to release this soon? 👀

[broofa]

@43081j 12.x will go out at the end of next month to allow for updating to TS 5.2 at the same time.. See #887