Support silencing sourcemap warning

[leo60228]

Example:

    plugins: [
        process.env.NODE_ENV == "production"
            ? terser()
            : prettier({
                  sourcemap: 'silent',
                  tabWidth: 4,
                  parser: 'babel'
              }),
        babel({ babelHelpers: "bundled" }),
    ],

[mjeanroy]

@leo60228 Thanks. Version 1.1.0 and 2.1.0 have been published with your commit ;)