reference all projections incl. d3-geo-projection and d3-geo-polygon

[Fil]

It's a lot, but we love projections, and it would be a shame not to find them with instant search.

I've put everything into a single file, but it's possibly too much. Leaving this as a draft for discussion:

We could:

• remove the d3-geo projections and split the remainder again into two groups (geo-projection vs geo-polygon), but that's still a long list and there are duplicates)
• create another type of classification? (polyhedral, etc)
• move the “additional methods” (geoProject…) in their own page, and have only projections in that page

[mbostock]

Only going to include the core modules for now.