Update user and admin docs, prepare for more screenshots

[jeffpaul]

What?

This pull request significantly updates the readme.txt file for the Two-Factor Authentication (2FA) plugin, enhancing user guidance and improving the documentation. Key changes include the addition of detailed setup instructions, descriptions of authentication methods, and answers to frequently asked questions (FAQs).

Enhanced User Guidance:

• Added comprehensive setup instructions for individual users and site administrators, including steps to enable and configure 2FA methods like TOTP, email codes, and FIDO U2F security keys (readme.txt, readme.txtL13-R91).
• Included security best practices, such as enabling backup codes and using multiple authentication methods for better protection (readme.txt, readme.txtL13-R91).

Improved Documentation of Authentication Methods:

• Provided detailed descriptions of each authentication method, including security levels, setup instructions, compatibility, and use cases (e.g., TOTP, email codes, backup codes, FIDO U2F, and dummy method) (readme.txt, readme.txtL13-R91).
• Highlighted HTTPS and browser compatibility requirements for FIDO U2F keys (readme.txt, readme.txtL13-R91).

Added FAQs and Clarifications:

• Addressed common questions, such as the absence of site-wide settings, account recovery options, and WebAuthn support. Linked to relevant GitHub issues for further details (readme.txt, readme.txtR123-R141).

Updated Visual References:

• Expanded the screenshots section to include new visuals, such as the TOTP setup QR code and backup codes interface, to help users better understand the plugin's features (readme.txt, readme.txtR123-R141).

Why?

Closes #699.

How?

Testing Instructions

Screenshots or screencast

Changelog Entry

Changed - Updated WP.org readme with additional user and administrative docs.

[jeffpaul]

@kasparsd related to your thoughts on #699, some questions:

• Should we perhaps link to https://wordpress.org/plugins/search/login+magic+link/ for folks looking for that functionality (at least until, if?, that's added to the 2fa plugin)?
• Should we link to https://wordpress.org/plugins/search/webauthn/ or more specifically to something like https://wordpress.org/plugins/two-factor-provider-webauthn/ and https://wordpress.org/plugins/wp-webauthn/ and https://github.com/mcguffin/two-factor-webauthn?

I'll update here once you weigh-in on those questions. I'll work on some additional screenshots to note what I added here as captions in this readme update.

[kasparsd]

This is great! Amazing work.

To answer your questions:

1. IMHO none of the magic-link plugins will work if the two-factor is enabled.

2. I suggest we link to https://wordpress.org/plugins/two-factor-provider-webauthn/ directly because it integrates specifically with the two-factor plugin and does it really well.

[kasparsd]

@jeffpaul I would like to merge this for the next release. Would you have time to iterate on it now or can we merge it as is and update later?

[kasparsd]

@jeffpaul Let me know if I can help with getting this ready for merge.

[masteradhoc]

@kasparsd checked this draft as well. i think this is quite good to be merged. if @jeffpaul doesnt have time to finish this one we could merge it and i'll take over the outstanding comments for him. what do you think?

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: kasparsd <kasparsd@git.wordpress.org>
Co-authored-by: masteradhoc <masteradhoc@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[jeffpaul]

@masteradhoc @kasparsd this is reasonably back and ready for your review