add working group charters

[HarHarLinks]

🎩 Vice Chair of the GB

To be considered in tandem with #2980 already merged and rebased

This PR should be additionally approved by another member of the GB before merging.

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[MTRNord]

I think this css screws with the events wg header on navigation:

scroll-snap-type: y proximity;
scroll-padding-top: 1.875rem;

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[HarHarLinks]

I think this css screws with the events wg header on navigation:

scroll-snap-type: y proximity;
scroll-padding-top: 1.875rem;

whats the issue here? screenshot/cap?