chore: make the repo commitizen-friendly

[stephengeller]

What does this change?

According to these docs, we haven't made our repository commitizen-friendly. This PR merges in the result of running commitizen init cz-conventional-changelog --save-dev --save-exact on the repo and setting up basic config.

This will enable everyone to use the proper commitizen cli in the CDK repo with cz, git cz or npm cz.

Does this change require changes to existing projects or CDK CLI?

Nope.

How to test

In the root of the repo, run npx cz and see the interactive menu work!

How can we measure success?

We can use npx cz with ease!

[github-actions]

🎉 This PR is included in version 4.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[akash1810]

Looks like we've moved to NPMv7 in this PR too as lockfileVersion in package-lock.json is now 2. Was this intentional? If so, shall we make a note of this in the README?

UPDATE: It looks like we're running NPMv6 in CI (see the build log on this PR) and I'm not sure if we're obeying the package-lock.json during the build as a result, so we'd also want to tell CI and CD to use NPMv7 too. It doesn't appear to be installed by default so we'd have to do something a bit horrible or stay on NPMv6 for now?