fix(q-p-w): Be explicit about the files and rm wasm-pack artifacts.

[abernix]

Following up on #270, this ensures that the correct files are included in the published @apollo/query-planner-wasm package.

Debugging this was frustrating, as npm has some particular rules about how it includes files and when it respects .gitignore vs .npmignore vs. the presence of both, but I'll point out that the suggestion to run npx npm-packlist provided at this URL was quite helpful.

Other references, which I've certainly read many times but still come in handy:

• https://docs.npmjs.com/cli/v7/using-npm/developers#keeping-files-out-of-your-package
• https://docs.npmjs.com/cli/v7/configuring-npm/package-json#files