README.md: be very explicit about podman machine setup requirements

More than one person has missed the link to the podman desktop
requirements that explain how to initialize podman machine.  Just copy
that setup directly inline here to avoid it being missed.

Signed-off-by: John Eckersberg <[email protected]>

Author: jeckersb

README.md

@@ -14,7 +14,8 @@ in alignment with the <https://github.com/containers/bootc> project.
 Requirements:
 
 - [bootc extension requirements](https://github.com/containers/podman-desktop-extension-bootc?tab=readme-ov-file#requirements)
-- (Even on Linux, you *must* set up `podman machine` with a rootful connection; see below)
+  - (Even on Linux, you *must* set up `podman machine` with a rootful connection; see below)
+  - `podman machine init --rootful && podman machine start`
 - qemu-system-x86_64/qemu-system-aarch64
 - xorriso/osirrox
 - golang