Add ⚡️ content to Common user flows - Remaining sections

[danielnordh]

Updates and addition of Lightning content to the relevant sections. From #470

Changes according to this doc: https://docs.google.com/document/d/1Fu-EPdUu9mK3Rsyk_yurWaxUdzGVV1gVD859XMqnQgY/edit?usp=sharing

Preview here: https://deploy-preview-501--sad-borg-390916.netlify.app/guide/designing-products/common-user-flows/

Once any feedback to content changes have been resolved I will re-order a few sections (recover, import wallet comes before securing a wallet etc.)

[Bosch-0]

Looking good, few minor comments left :)

[GBKS]

LGTM. There are some open comments that I have no strong opinion on, so I will not leave an approval for now.

I think we have to come back to this page later once the onboarding and payments sections are further, and our recommendations around Lightning are more refined. For example, do our recommendations assume that a wallet uses LNURL, keysend and Lightning addresses? If so, then we can describe much smoother payment UX than without those techniques.

[sbddesign]

Good additions.

I left some nit-picky grammar, spelling, and punctuation edits.

Additionally, I raised some discussion points around a few things like elevating the LN content and whether or not an LN wallet can be "switched".

[pavlenex]

LGTM, I'd just add that we probably should create a new issue to add Child Pay For Parent (CPFP) in the glossary and link to this page, as RBF isn't the only way to bump a fee, but since CPFP isn't in the glossary, I'll open a new issue to address this and update the page at the same time.