Update the ZK Email Stamp description

[lebraat]

The ZK Email Stamp is going to require additional details to make sure users know what to expect when verifying the Stamp.

We need to change this Stamp type to include the step-by-step guide section, with the following details:

Step-by-Step Guide
Step 1: Click the “Check Eligibility” button below to kick off the verification process.
Step 2: Log in to your Google account, and provide zkEmail the permissions to scan for purchase confirmations and service receipts while keeping your data private.
Step 3: zkEmail will scan your inbox, archive, and tagged emails for evidence of your Amazon and Uber activity, and will assign you credentials based on that usage.

Important considerations:

• We only scan your inbox, archive, and tagged emails. Any deleted emails will not count towards this Stamp
• This Stamp uses zero-knowledge proofs to analyze emails without exposing personal data
• This Stamp only scans for specific purchase confirmation and receipt patterns
• No personal information or email content is stored or shared