Remove s3 logic and load html email templates from local asset directory

[nickviola]

🗣 Description

Removes s3 logic and references locally mapped assets.

💭 Motivation and context

Asked to remove s3 logic and reference assets locally.

🧪 Testing

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

[cduhn17]

LGTM

[ameliav]

There's a couple console logs but Nick explained why they are there so LGTM!