Replace static CSS/script imports with Drupal placeholder tokens

[greg-does-weather]

What does this PR do? 🛠️

• Defines libraries in our theme so we can import them via name
  • uswds-init is for the init script, so we can specify that it goes in the head
  • uswds-customized for our built styles.css and the USWDS scripts
  • location-search for powering the location search
  • localize-timestamps for powering localization of timestamps
• Updates our theme to, by default, import the two USWDS-related libraries on every page
• Updates our html.html.twig template to remove the static <link> and <script> tags
• Manually attach the location-search and localize-timestamp libraries in the twig templates that need them, so they only get loaded on relevant pages

Going forward, if there are scripts that only need to appear in certain places, this may be a template for how we can do that.

closes #234

What does the reviewer need to know? 🤔

make cc may be enough, but the theme cache has to be cleared out in order for Drupal to re-read the libraries stuff.

Screenshots (if appropriate): 📸

n/a because nothing should have changed from the user's perspective

[eric-gade]

Just a quick approval without checklist here -- this looks good to me. Good that location search is now only on the relevant pages.