attribution and license for illustrations

[vykster]

• Determine license for illustrations
• Update site to reflect license and attribution to illustrator

[machikoyasuda]

@mrose914 @vykster Who should be attributed as credit for the illustrations on calitp.org?

This is the main illustration on the site:

There are also a few small icons.

Would be great to knock out this ticket (or close it entirely) before it turns 3 years old.

[cal-itp-bot]

Chris Arvin for the main illustration. I believe Colleen Corcoran did some of the newer ones.

[machikoyasuda]

@mrose914 Perhaps this can be turned into a small ticket and marked as Stretch for the next sprint?