Update dependencies that require ESM

[nolanlawson]

Right now we have several dependencies that we can't update, because they rely on ES Modules rather than CommonJS:

• parse5
• estree-walker
• webdriverio

(For webdriverio it's less severe, since it's only a devDep.)

I see two options for solving this:

1. Drop CommonJS support in Node packages, use "type": "module" #3017
2. Bundle these dependencies into our dist files (e.g. with Rollup)

#1 would be the simplest solution, but it's a breaking change. And I'm not sure how realistic it is, given Jest's lack of mainstream support for ESM. (E.g. would it even be possible to import @lwc/compiler into a jest.config.js file, if it's "type": "module"?)

#2 is kind of gross, but may be the most pragmatic solution. We can continue to ship both CJS and ESM as we do today, without breaking downstream consumers of our npm package.

[nolanlawson]

A third option is to use dynamic import() to import the ESM package from CommonJS. But this seems unfeasible given that we expose synchronous APIs. (Or our async APIs are deprecated, e.g. transform is deprecated in favor of transformSync.)

[nolanlawson]

We have already effectively started doing this, by bundling deps directly into our output.

The last one we haven't done yet is estree-walker.