doc: add strategic initiatives from TSC repo

This (along with a corresponding PR for the TSC repo) moves the strategic initiatives from the TSC repository to the main core repo. This will increase visibility for strategic initiatives. It will also facilitate the proposed reduced centrality of TSC champions to strategic plans.

In the process, I made the text less wordy. I moved the Build Resources initiatve out of the active list, as discussed at the most recent TSC meeting. I alphabetized the table entries. (Chronological order isn't obvious to a reader if no dates are provided.)

Refs: https://github.com/nodejs/TSC/issues/962#issuecomment-880233678