Update index.html.md

Resolves #1913 (closed)

@stanhu I reordered them in my (perceived) order of priority, but I'm not sure which I should remove, if any.

I think that "Ship first GraphQL endpoint" is most likely to slip; "all" in "Make sure all Platform backend community contributions are merged, closed, labeled “awaiting feedback”, or taken over by us and in active development" may be optimistic; and "60" in "Close 60 Platform backend bug issues" definitely is, unless we add new people to the team very quickly, but KRs should be challenging, right?

I think it's better if we keep the current list and hit 80%, than if we remove a few items and hit 100%. All of these are (in my mind) top priorities for Q1, and I'd rather miss a few and move them to Q2, than remove them entirely and risk forgetting about them.