Charter: allow formally for WG co-chairs

[platipodium]

Currently, it says:

"Working Groups self organize, with support from the Executive Committee, and nominate a Working Group Chair, for approval by the Members Council."

Suggestions is to rephrase:
"Working Groups self organize, with support from the Executive Committee, and nominate a Working Group Chair and optionally a Co-Chair, for approval by the Members Council."

[aaraney]

For context, here is link to the current text mentioned above.

[platipodium]

Karin says: "A Co-Chair model has several advantages and there are various Good Practice examples. (i) Diversity; (ii) Redundancies; (iii) Chance to guide the Group together and having exchange on coordination questions"

[platipodium]

Mark says: "A Co-Chair model has several advantages and there are various Good Practice examples. (i) Diversity; (ii) Redundancies; (iii) Chance to guide the Group together and having exchange on coordination questions"

[LuS-GitHub]

I would suggest taking out the "optional" language

[alee]

added co-chairs language to working groups in #388