Banner fix

[kolchfa-aws]

Closes #2809

This PR accomplishes the following:

• Overlays the banner text over the image and adds responsiveness to the image and text
• Refactors button classes to extract common code for easier aggregation
• Adds a darker blue button to use for light-colored images for sharper contrast
• Removes padding from a button icon to align it with the button text
• Shortens the "Contribute" hero heading to avoid a scroll bar and covering of the text by the button on mobile screens
• Keeps the aspect ratio for author photos on author cards

Check List

• [x] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the BSD-3-Clause License.

[nateynateynate]

Spot on Fanit. This works great.