Add configPlugin option to @nx/rollup:rollup executor

[oliveryasuna]

Not sure how often this feature is utilized, but I use the Rollup's --configPlugin option to specify @rollup/plugin-typescript in order to write my Rollup config in TypeScript.

Either --configPlugin typescript or --configPlugin @rollup/plugin-typescript.

It would be useful if the executor supported an option named configPlugin.

For now, I will write my Rollup configs in JavaScript and use JSDoc type hints.

[dfbaskin]

This was helpful discussion about @rollup/plugin-typescript vs rollup-plugin-typescript2.
rollup/plugins#541