Update CONTRIBUTING.md for Specification Project's repositories

[kwsutter]

Create/Update CONTRIBUTING files

Per input from the Eclipse EMO, each Specification Project needs to ensure that a CONTRIBUTING.md or CONTRIBUTING.adoc file exists in each specification-related repository maintained by Specification Projects.
In addition, the CONTRIBUTING.md or CONTRIBUTING.adoc file needs to include the following text:

## Eclipse Development Process

This Eclipse Foundation open project is governed by the Eclipse Foundation
Development Process and operates under the terms of the Eclipse IP Policy.

The Jakarta EE Specification Committee has adopted the Jakarta EE Specification
Process (JESP) in accordance with the Eclipse Foundation Specification Process
v1.2 (EFSP) to ensure that the specification process is complied with by all
Jakarta EE specification projects.

* https://eclipse.org/projects/dev_process
* https://www.eclipse.org/org/documents/Eclipse_IP_Policy.pdf
* https://jakarta.ee/about/jesp/
* https://www.eclipse.org/legal/efsp_non_assert.php

Please do this at your earliest convenience.
Thank you!

-- EE4J PMC (ee4j-pmc@eclipse.org)