Add two LN related user-researches

[pavlenex]

Added two user-researches that I've read through and verified.

Arcane's LN research has been added earlier.

If anyone has any more that I should add, let me know.

closes#486

[Bosch-0]

LGTM!

[GBKS]

Not Lightning, but we should also add Patricia's latest research.

Only criticism would be that the Lightning scaling report is not directly user-research, but more of a technical analysis. But it's still relevant to users (fees), so we should keep it.

[pavlenex]

@GBKS I remember Patricia's long-term goal with it is to integrate the research within the guide. Is this still something we'd like to pursue? If so, how do you envision such integration?

I'll add a link to Patricia's website instead of GH, I think it better presents information visually.

[GBKS]

@pavlenex nice, I wasn't aware she had even posted her research results on the web (was only aware of the repo).

Ideally, we could integrate her results more closely into the guide. A good starting point could be to identify key quotes from each persona and insert them into relevant pages. Also, the Getting to know your users page is currently relying on a made-up persona, maybe this could be refreshed with a persona Patricia identified?

[GBKS]

ACK. Looking good. Thank you for taking this one on.

[pavlenex]

Two approvals and this one was trivial, so will merge it. Thanks for prompt reviews gents. 🎩