docs: add Firecracker logo + title image
docs: add Firecracker logo + title image

Signed-off-by: Radu Weiss <e20b2d982c117e9298ee475ba7241e3f2127299b@amazon.com>
firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker