Creating new section for TAM emails in existing Docs page

What does this MR do?

Per @sselhorn I'm adding the digital onboarding TAM emails to this page. The purpose is to put everything the onboarding customer needs into one place. It should be easy to find, easy to search, and provide more task-based (in this case, checklists) assistance.

Related issues

Author's checklist (required)

• Follow the Documentation Guidelines and Style Guide.
• If you have Developer permissions or higher:
  • Ensure that the product tier badge is added to doc's h1.
  • Apply the documentation label, plus:
    • The corresponding DevOps stage and group labels, if applicable.
    • development guidelines when changing docs under doc/development/*, CONTRIBUTING.md, or README.md.
    • development guidelines and Documentation guidelines when changing docs under development/documentation/*.
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  • Request a review from the designated Technical Writer.

Do not add the feature, frontend, backend, ~"bug", or database labels if you are only updating documentation. These labels will cause the MR to be added to code verification QA issues.

When applicable:

• Update the permissions table.
• Link docs to and from the higher-level index page, plus other related docs where helpful.
• Add the product tier badge accordingly.
• Add GitLab's version history note(s).
• Add/update the feature flag section.

Review checklist

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• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

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For suggestions that you are confident don't need to be reviewed, change them locally and push a commit directly to save others from unneeded reviews. For example:

• Clear typos, like this is a typpo.
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3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set.
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