Document Snaps transaction insights

[alexandratran]

Description

Add feature page for transaction insights. Also reorder feature cards on index page in alphabetical order, and make minor changes to related content for consistency and simplicity.

Issue(s) fixed

Fixes #1260

Preview

https://docs.metamask.io/1260-txn-insights/snaps/features/transaction-insights/

Checklist

Complete this checklist before merging your PR:

• [x] If this PR contains a major change to the documentation content, I have added an entry to the top of the "What's new?" page.
• [ ] The proposed changes have been reviewed and approved by a member of the documentation team.

[github-actions[bot]]

Preview published: 1260-txn-insights

[github-actions[bot]]

Preview published: 1260-txn-insights

[github-actions[bot]]

Preview published: 1260-txn-insights