doc: update maintainers in README.md (#478)
doc: update maintainers in README.md (#478)

This commit modifies the structure of the README.md to add a markdown
heading. This change is motiviated by the CLO tool provided by CNCF.
This repository is failing a check for maintainers as you can see on
the dashboard:
https://clomonitor.io/projects/cloudevents/cloudevents#sdk-javascript

Documentation for this change can be found here:
https://github.com/cncf/clomonitor/blob/main/docs/checks.md#maintainers

Signed-off-by: Lance Ball <637094cbcafd6c4c397ebad24eca1a25fa2cf312@redhat.com>
cloudevents/sdk-javascript,cloudevents/sdk-javascript