Support tsconfig as file path

[gauntface]

I'm working on a project that has Typescript code for browser and Node environments. Each have seperate tsconfig files.

The current logic looks like it searches for a tsconfig.json file in the current working directory, meaning I can't use a different config file in a subdirectory.

Would you be open to using tsconfig option as a boolean or string path?

plugins: [
      typescriptPlugin({
        tsconfig: path.join(__dirname, 'src', 'client', 'tsconfig.json'),
        typescript: require('typescript'),
      }),
    ],