changed hardcoded email text to site reference [issue #235]

[Brorean]

In the site footer changed hardcoded email text to a variable site.email. This is for issue #235.

[jordangov]

Thanks @Brorean ! We appreciate the PR. We'll need to have you sign the CONTRIBUTORS.md file before we can accept the PR, and we do have a PR template that seems to have gotten lost here. Can you please pull that in and check of the items as you've completed them?

I know this is a small change, but we're trying to make sure we can have a solid process for all contributions.

[Brorean]

Checklist

I have…

• [*] run the application locally (./scripts/serve) and verified that my changes behave as expected.
• [*] run the build process locally (./scripts/build) and make sure it builds correctly.
• [*] run the test suite (./scripts/test) and verified that all tests pass. For some reason the test fails on my virtual machine on ./public/how-to-open-source.html with error External link https://code.gov/about/compliance/inventory-code failed: 404 No error**
• [*] summarized below my changes and noted which issues (if any) this pull request fixes or addresses.
• [*] thoroughly outlined below the steps necessary to test my changes.
• [*] attached screenshots illustrating relevant behavior before and after my changes.
• [*] read, understand, and agree to the terms described in CONTRIBUTING.md.
• [*] added my name, email address, and copyright date to CONTRIBUTORS.md.

Summary of Changes

Changed the site footer to use site.email instead of hard coded value.

Testing

Start server using ./scripts/serve and open in web browser. Scroll to the footer in the page and verify that the code@dds.mil email address appears. Click on page and view source. Scroll to the footer and verify that the reference uses {{site.email}}.

Screenshots

Before:

After:

[jordangov]

Thank you so much! Really appreciate the effort, and feel free to hack on anything else ;)