fix: give stats initial values

[achingbrain]

Otherwise the compiler cannot derive the type and thinks stats.snapshot returns {}

[achingbrain]

The resulting types:

    /**
     * Returns a clone of the current stats.
     */
    get snapshot(): {
        dataReceived: Big;
        dataSent: Big;
    };
    /**
     * Returns a clone of the internal movingAverages
     */
    get movingAverages(): {
        dataReceived: MovingAverage[];
        dataSent: MovingAverage[];
    };