Jetpack Carousel: automate the generation of the custom swiper.js library build

#### Describe the solution you'd like
Work is currently [underway to use the swiper.js library to provide the slider functionality within the Carousel module](https://github.com/Automattic/jetpack/pull/20107).

Currently [a custom build is being generated](https://github.com/Automattic/swiper) of the library in order to shave 100KB off the uncompressed library size. The disadvantage of this approach is that there are no automatic notification of dependency updates as there would be if the full library was included as an npm dependency.

Ideally we need a way to get the reduced size of the custom build, with an automated process for generating new release builds when the dependency is updated.

Review the custom swiper.js build linked in the issue and the Carousel work in PR 20107 first. Determine how dependency updates can trigger a reduced-size release build; done when updated swiper.js dependencies automatically produce the custom library build.

Written by the indexing model from the issue text.