Add campaigns timeline to homepage

[LanesGood]

Add timeline of all campaigns to CASEI homepage.

From previous discussions:

This is probably the 'lowest hanging fruit' location to plop a plugin like this without reinventing the design of the website. But whereas the homepage items currently create a filter on the Explore page, this would direct users directly to a campaign itself.

Things to explore:

• What is easy to customize vs. what is fixed with this plug in? For example, does it need to use the same fonts and colors? As it is, I don't think it really matches the style of CASEI and looks like a plug in. But you might be limited to what can be changed.
• What information about a campaign should be surfaced here? You wouldn't want to add too much about a campaign, you'd want to direct people to read more on the actual campaign page. Perhaps limiting this to the same information on a campaign "card" in the explore page will be sufficient.

Parent ticket: https://github.com/NASA-IMPACT/ADMG-project/issues/1066

[LanesGood]

Explore using library instead of auto-generated timeline js instance:
https://timeline.knightlab.com/docs/instantiate-a-timeline.html

[LanesGood]

We are exploring building out the JSON within the frontend application, rather than using the google sheet, to allow for a few things:

• Relying on the internal API URLs to avoid running into content-security-policy issues, which are currently blocking loading the images from external URLs
• Avoiding needing to build in the knight lab’s google sheets proxy to the content security policy exceptions
• Avoiding needing to trigger a google collab > google sheet > casei integration each time a new campaign is added

Building the json internally in the application may also allow us to more quickly iterate on additional text fields, links, etc.

cc @EJwalker13