Grid cards for Technology and Research sections
# Tasks
* [x] Add grid cards at the:
* [x] [Technology intro][] page.
* [~] [Research intro][] page.
Not doing right now: the [Onion Plan][] documentation is not currently structured
with `README.md` files in most of it's sections. That's a requirement for having
a clean grid list of sections.
[Technology intro]: https://onionservices.torproject.org/technology/
[Research intro]: https://onionservices.torproject.org/research/
[Onion Plan]: https://gitlab.torproject.org/tpo/onion-services/onionplan
# Time estimation
* Complexity: negligible (0.1 day)
* Uncertainty: low (x1.1)
* [Reference](https://jacobian.org/2021/may/25/my-estimation-technique/) (adapted)
issue