[ADD] Added code snippets for Alchemyst Retriever

[anuran-roy]

Overview

Type of change

Type: [Replace with: New documentation page / Update existing documentation / Fix typo/bug/link/formatting / Remove outdated content / Other]

Related issues/PRs

• GitHub issue:
• Feature PR:

• Linear issue:
• Slack thread:

Checklist

• I have read the contributing guidelines
• I have tested my changes locally using docs dev
• All code examples have been tested and work correctly
• I have used root relative paths for internal links
• I have updated navigation in src/docs.json if needed
• I have gotten approval from the relevant reviewers
• (Internal team members only / optional) I have created a preview deployment using the Create Preview Branch workflow

Additional notes