Follow conventional commit instead of Node.js convetion

[mmarchini]

Conventional Commit is a set of commit message guidelines used by many projects. The main advantage of this instead of using the Node.js commit convention is tooling: Conventional Commit has a lot of community tooling readily available to check commit messages and prepare releases. Comparing to node-core-utils, using conventional commit should make it easier for us to manage the project, allowing us to land via GitHub interface (we lose commit metadata, but I think that's fine for llnode) and we can use release-please to prepare releases automatically (we still need to publish to npm manually though). Not only that, node-core-utils is very nodejs/node focused, and keeping it multi-project makes ncu harder to maintain.

So I propose we switch the commit convention on the project to use conventional commit. cc @nodejs/llnode @nodejs/diagnostics