Move `microsite-templates` into this repo

[natemoo-re]

Currently microsite-templates live in their own repo. This was just to make using degit as simple as possible but it would be better to have everything in this repo.

[eyelidlessness]

This seems like something that might benefit from a package manager that speaks monorepo by default (PNPM or Yarn which I’m still using but still hesitant to recommend for previously detailed reasons). When I’ve offered PRs here my flow is to lerna bootstrap --hoist to validate against either the example projects or my own, but at least for internal usage the other package managers should handle this case transparently (I know yarn does).

It would definitely be a little less friction though to have everything in one repo.