What naming convention do I use for scripts in package.json?

Please always use kebab case. The colon is a throwback to gulp, and it looks terrible. I hate it.

Disclaimer: My opinions are often wrong.

There is no official naming convention. Before npm@v4 standard scripts had only one word, for example test, start, prestart. npm@v4 introduced a new script prepublishOnly*.

So now, the best practice is use lowerCamelCase.

*Reference: https://iamakulov.com/notes/npm-4-prepublish/