refactor: use Canto asset for homepage

[alexgoff]

Test with: lsst-epo/rubin-obs-api#311

This refactor adds a field to the homepage for a hero image loaded from Canto. If the Canto asset is specified, it will override any Google asset.

Adds the following to the client:

• basic typings for Canto responses
• Canto image used for homepage OpenGraph
• extend homepage server tree so that image element is rendered on the server and can begin client load immediately
• use Canto resizes to generate a srcset that browsers can use to determine if a smaller image size can be used (mostly for mobile)
• uses Canto 100px size as a placeholder image

To test:

• In Craft
  • Select a new hero image in the Canto field on the homepage
• On client
  • Go to homepage
  • See that new image is in the hero
  • See that new image is in the OpenGraph tags in the header
  • Check the network tab, there should be a request under img for 2050, which is the largest Canto resize and the most likely to be loaded on a desktop since our page is fixed at 2000px wide.
  • Reload the page with a mobile device (Pixel 7 or an iPhone) selected from responsive mode
    • Check the network tab, see that a smaller size request was made (it will probably be 800)
  • Feedback
    • any noticeable performance difference between previous image and the new Canto image?
    • is the low-res 100px placeholder image working well as a placeholder, or is it distracting?