FeatureReportByteLength of blink(1) is 9 instead of 8

Tried to get caps via [`HidP_GetCaps`](https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/hidpi/nf-hidpi-hidp_getcaps) API on Windows, and it turned out that `FeatureReportByteLength` is **9**, which is different from the [doc](https://github.com/todbot/blink1/blob/main/docs/blink1-hid-commands.md):

> The blink(1) feature report packet is 8 bytes long.

Why?