feat: add a defineConfig utility function and use it in examples

[haoqunjiang]

This commit also exports the createConfig as a named export for consistency in import styles.
I feel that though the name is descriptive enough, it's not a suitable name to be used directly in the defineConfig arguments, so I used import aliases in all examples.

typescript-eslint 8.15 added support for infinitely deep array nesting in the config helper, so I removed all the spread patterns in the examples. typescript-eslint/typescript-eslint#10333

As discussed in vuejs/create-eslint-config#37

/cc @segevfiner

[haoqunjiang]

Gonna need it in my @vue/eslint-config-standard-with-typescript refactor so I'm merging it.