prepareContext(contextOptions) {
    this.helpWidth = this.helpWidth ?? contextOptions.helpWidth ?? 80;
  }
prepareContext is called by Commander after applying overrides from `Command.configureHelp()`
and just before calling `formatHelp()`.

Commander just uses the helpWidth and the rest is provided for optional use by more complex subclasses.

@param {{ error?: boolean, helpWidth?: number, outputHasColors?: boolean }} contextOptions