Export dashboards

[cbaxley]

🗣 Export Dashboards

This adds a script to export the dashboards from Kibana.

💭 Motivation and context

It is difficult to know if changes to the dashboards will be overwritten or match the initial state of the install. Therefore exporting them will allow for backup, testing, and adding of dashboards.

🧪 Testing

I was able to follow the readme and export dashboards both from a Linux host and a Windows client.

✅ 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.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[mreeve-snl]

LGTM