Clarify Stage 0 proposals requirements

[Ginden]

I'm not sure where this issue should be, but:

• tc39/proposals/stage-0-proposals.md claims that champion is required for stage 0 proposal
  • [Stage 0 proposals] are "planned to be presented to the committee by a TC39 champion"
  • All stage 0 proposals have TC39 champions
• tc39/proposals/README.md links to tc39/process-document as authoritative
• tc39/process-document/index.html claims that champion is required for stage 1 proposal.
  • Champion must be identified to advance to stage 1
  • No champion is required for stage 0
• tc39/ecma262 agrees with tc39/proposals/stage-0-proposals.md.

Some of these documents should be fixed, and I'm not sure which ones.

[ljharb]

I'd say it's the process document. The committee has been very clear that non-members can not bring any proposal without a member sponsoring it. Note, however, that's not necessarily the same as a champion.

In other words, stage 0 does not require a champion, but it still requires a TC39 member's cooperation.

[ljharb]

Closing in favor of tc39/process-document#11