How to use the @plumier/core.response.file function in @plumier/core

async execute(invocation: Readonly): Promise {
        const uiPath = this.opt.endpoint.toLowerCase() + "/index"
        if (invocation.context.path.toLowerCase() === "/swagger.json")
            return response.json(this.spec)
        if (invocation.context.path.toLowerCase() === this.opt.endpoint.toLowerCase())
            return response.redirect(uiPath)
        if (invocation.context.path.toLowerCase() === uiPath)
            return response.file(join(dist.getAbsoluteFSPath(), "index.html"))
        else
            return invocation.proceed()
    }
}