Anyone who contributes through pull requests, responses to issues, documentation or otherwise, is a contributor.
Maintainers have commit permissions. They are responsible for creating release commits. Finally, they are responsible for closing out issues that are duplicates, not reproducible or otherwise should not be addressed. New maintainers are added by existing maintainers at their discretion. If you want to become a maintainer, start by looking at the issues and current open pull requests. You can triage existing issues, provide fixes, and/or create issues that will improve the packages for the community at large. You can view the current list of maintainers in the Javascript Github group.
A code owner is a maintainer with an extra level of commitment. Code owners are expected to make themselves available to review pull requests and discuss architectural or core code changes. Code owners also have veto power over "core" package changes, which we define here as breaking change or major refactors to the plugin engine or the cli. Code owners are a small group by design, and new code owners will be added only rarely. Code owners are listed in the Javascript Github group.
Different levels of consensus are needed for different kinds of changes. For small PRs, it is sufficient to get the two approvals you need to merge the PR.
For major design additions or refactors, it is more important to get buy-in from other contributors before starting. Post in the Discussions, and allow a few days for other contributors to weigh in. Your goal here is to 1) get feedback on your plan before investing the time in a PR and 2) to get buy-in from other contributors. Once you have addressed blocking feedback and received some buy-in, you are ready to proceed with code changes.
Roadmap changes require a lengthier discussion: when you propose a roadmap change, allow at least a week for as many maintainers as possible to respond. Your goal here should be to get buy-in from all maintainers (with silence interpreted as approval). In rare cases, there may prove to be irresolvable disagreement between maintainers, in which case it is acceptable to conduct a majority vote.