oneDPL project makes and records decisions in public

[rodburns]

Publish and follow a process for RFCs to ensure that the community has the opportunity to comment and contribute to changes, features and other proposals for the project.
The oneDNN project implements a RFC process that has been operating for a while and can be used as a template or guide.

Acceptance Criteria:

• A process has been reviewed by the team and published on the project repo describing the process for RFCs
• The process is being used by the oneDPL project team

[akukanov]

PR review: oneapi-src/oneDPL#1878
Update: the patch is merged.