Clarify who votes in Jupyter Executive Council elections

[choldgraf]

Somebody asked me who gets to vote for the Jupyter Executive Council elections, and I couldn't find it anywhere obvious in the Governance documentation. This is where I assumed it would be listed just for reference.

For reference, I was told that the answer is "Members of the Union of Councils".

I think this means members of:

• The Executive Council
• The Steering Council of any Jupyter sub-project
• The Software Steering Council

When I searched for "Union of Councils" I also didn't find anything really obvious either, so I think we should document that someplace clear as well.

[rpwagner]

@choldgraf I think the working definition is on the Executive Council page.

The EC will consist of 6 Council members who serve 2-year terms. Members are elected from the body of the union of all Standing Committee, Working Group, and Subproject Councils (“Union of Councils”, UoC).

It would be clearer to have a clearer definition on the Governance Overview page, such as

## Union of Councils

The Union of Councils (UoC) is the union of the membership of all Standing Committee, Working Group,
and Subproject Councils. The UoC votes on the membership of the [Executive Council](<ref to EC page>)
and may be asked to vote on other Project-wide topic when appropriate.

Then the previous two sentences would become:

The EC will consist of 6 Council members who serve 2-year terms and are elected by the 
[UoC](<ref to UoC anchor on governance page>).

[jasongrout]

I've drafted a governance PR (#252) that tries to incorporate suggestions from this discussion and jupyter-governance/ec-team-compass#23.