USWDS-Compile - Feature: Update references to Gulp 5

[thisisdano]

Is your feature request related to a problem? Please describe.

As of uswds-compile 1.2.0, we're using Gulp 5. Let's update any references in the README and elsewhere from Gulp 4 to Gulp 5.

Describe the solution you'd like

I know this needs to happen in the README and in the repo description. There may be more places.

Current README:

Simple Gulp 4.0 functions for copying USWDS static assets and transforming USWDS Sass into browser-readable CSS.

Current repo description:

Simple Gulp 4 functions for copying USWDS static assets and transforming USWDS Sass into browser-readable CSS.

These should both now say Gulp 5 (not Gulp 5.0).

Describe alternatives you've considered

No response

Additional context

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct.
• [X] I checked the current issues for duplicate feature requests.

[thisisdano]

Note that we'll need to update the repo description after we publish the release. We modify in the GH interface, not through a PR.

[brunerae]

Completed with PR #117