Process for ELISA working group activities

[reiterative]

Document a generic process for ELISA working group activities, to facilitate collaboration and coordination between groups and make it easier for newcomers to ELISA to understand the context and results of a given activity.

An initial set of guidance notes is drafted in the WIki here:

https://github.com/elisa-tech/wg-osep/wiki/Process-for-ELISA-working-group-activities

The intended outcomes are to:

• a) Apply it to an example topic / activity,
• b) Write up the process in a PR, for inclusion in the repo
• c) Write up the results of a) in a PR, for inclusion in the repo alongside b) as an illustration