Update pebble cards homepage

Changed a few things for the homepage:

[Header interaction changes]
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. Removed header opacity change
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. Added background image parallax
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3. Tweaked watch parallax to be more subtle
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4. Added bottom edge gradient to lessen the visual edge

[Footer improvements]
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. Removed footer margin-top to make room for the press section
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. Changed the background color to match the app store image
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3. Centered app store image

[Press mention section added]
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. Created press mention brand images
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. Added press images to the section with proper styling
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3. Added mobile css for press section



`background-color: black;`