Implements a new homepage page template using new CSS system

[djanelle-mit]

This work implements the LNHU project new homepage for Wordpress. This PR contains the following:

A new CSS system
There's a new v2 styling system that contains a similar structure to our SASS setup: a central v2 file that pulls variables, component styles, partial styles, and page specific styles into a single CSS style sheet. This work was done to take advantage of new CSS features and decouple us from needing to compile SASS. The styles in here are built to work alongside the current global css sheet (compiled from SASS). Eventually we'll need to strip away the global style sheet and patch holes that are cascading down into the v2 styles.

New homepage template
We're introducing a v2 version of the homepage template that also includes a v2 header and v2 footer. This is structured to be able to merged into production alongside our current homepage but be swapped over on launch day. This template preserves the visuals of the current header, navigation, and footer, but introduces a wider container width. Because of this, the header and footer styling was slightly rebuilt to adjust to a new typography scale and the container width change.

Static homepage content
We're launching with static content. Only the hours will be dynamic. In a future series of PRs we'll make each block of this new homepage editable in an incremental fashion. A future PR will also include the true go-live content for launch day.

Hours enqueued
To avoid needing to refactor the hours plugin, this work enqueues the hours-loader.js file directly on this page. This uses the plugin's behavior and requires the plugin to be installed, but avoids duplicating the logic for a single page.

LibChat
In the "Using the Libraries" section there's an Ask us box that includes a new LibChat widget. We've customized the offline and online images to fit the new design better.

Search widget plugin
This work contains a new option available for the search widget we use to display the search box. A "Unified Search v2" option now removes excess markup and introduces a new set of markup for the new homepage. This doesn't affect the previous work we did to introduce the Unified Search (v1) option and can coexist with v1.

Developer

Stylesheets

• Any theme or plugin whose stylesheets have changed has had its version
  string incremented.

Secrets

• All new secrets have been added to Pantheon tiers
• Relevant secrets have been updated in Github Actions
• All new secrets documented in README

Documentation

• Project documentation has been updated
• No documentation changes are needed

Accessibility

• ANDI or Wave has been run in accordance to
  our guide and
  all issues introduced by these changes have been resolved or opened as new
  issues (link to those issues in the Pull Request details above)

Stakeholder approval

• Stakeholder approval has been confirmed
• Stakeholder approval is not needed

Dependencies

YES | NO dependencies are updated

Code Reviewer

• The commit message is clear and follows our guidelines
  (not just this pull request message)
• The changes have been verified
• The documentation has been updated or is unnecessary
• New dependencies are appropriate or there were no changes