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

PR-URL: https://github.com/nodejs/node/pull/39394


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>