workbox-build 6.2.2 on Node.js NPM

Workbox v6.2.2 fixes a few bugs introduced in the v6.2.0 release.

🐛 What's Fixed?

Validation fix for plugin functions passed to runtimeCaching in the build tools. [#2901]
Ensure that our tsc configuration transpiles newer language features down to the ES2017 target level. [#2902]
Update to our lerna configuration to use the --exact tag when publishing to npm, to ensure that all the mutual dependencies in the monorepo use exact version matches, and not ^ versions. [#2904]