Update README file with a summary of EEA Process

[jpradocueva]

It is suggested to add the following content to the README file.

This aims to provide a summary of how to to submit an EEP.

EEA Structure

• Indicate that each WG has its own branch.

EEA Overall Development Process

• Provide an explanation of the above diagram.

Use Case Creation Process

• Provide an explanation of the above diagram.

EEP Creation of Documentation Process

• Provide an explanation of the above diagram.