function getResolution(h3Index) {
    const [lower, upper] = h3IndexToSplitLong(h3Index);
    if (!H3.isValidCell(lower, upper)) {
        // Compatability with stated API
        return -1;
    }
    return H3.getResolution(lower, upper);
}
Returns the resolution of an H3 index
@static
@param  {H3IndexInput} h3Index H3 index to get resolution
@return {number}          The number (0-15) resolution, or -1 if invalid