Get CSS/scss working for SDC

Problem/Motivation

The ticket ✨ Create USWDS Alert single directory component Active added scss when it created the component, however the SCSS does not seem to be being used. This is likely because we are not rendering the content with the rest of the site, only adding it via JS. There is also the complication that proper styling may involve other classes beyond the scope of the USWDS alert. This may be delicate and require some hard choices.

Acceptance Criteria

1. CSS works.

Proposed resolution

Remaining tasks

Steps to reproduce