[DOC] Easy onboarding solutions

[PiVortex]

Background

It is not clear which easy onboarding solutions there are for NEAR, as in social login with email or password.

Fast auth is being worked on and there is also apparently web3auth, I wonder if there are any other solutions. We have quite a few developers asking for these solutions. We should add them to the docs.

User Stories

• As a user, I want to easily find which onboarding solutions there are on NEAR

Acceptance Criteria

• [ ] Gather information on existing onboarding solutions
• [ ] Make them explicit in the "integrations page"

[PiVortex]

https://github.com/vex-labs/web3-auth-usage Good starting point wallet selector + web3auth + mtx