Consider defining what a technical plenary is and setting requirements related to it

[hober]

(This is essentially the counterpoint to w3c/process#1094)

It's probably a bit surprising to a casual reader of the Process document that the concept of a technical plenary, or of TPAC, nowhere appears in the document. I suspect many members expect part of their annual dues to be used to fund W3C's premier annual event, so perhaps the Process document should make that expectation explicit.