Update Documentation on Creating a Raspbian Image

[theGOTOguy]

I found that I am unable to mount the ostensibly ext4 Linux partition generated by Pi-Gen.

At first I thought that maybe this was because of this bug with 64-bit hosts but even the Dockerized build process seems to produce images that I can't mount.

Relevant output of sudo fdisk -l:

Disk /dev/sdf: 59.48 GiB, 63864569856 bytes, 124735488 sectors
Disk model: MicroSD/M2      
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x9cdfcf86

Device     Boot  Start     End Sectors  Size Id Type
/dev/sdf1         8192  532479  524288  256M  c W95 FAT32 (LBA)
/dev/sdf2       532480 3932159 3399680  1.6G 83 Linux

Relevant output of sudo mount /dev/sdf2 /mnt/simpleaq:

mount: /mnt/simpleaq: wrong fs type, bad option, bad superblock on /dev/sdf2, missing codepage or helper program, or other error.

It is noteworthy that I can mount the boot sector, /dev/sdf1.

@bensonk, is it clear to you what I might be missing here? Feel free to try this procedure with one of the build artifacts yourself and see if you can mount the Linux partition.

[theGOTOguy]

Ok, whatever the problem is: it also exists on the official RPiOS lite build. Maybe this is just a question about what the correct mount command is.

[theGOTOguy]

Ok, I confirmed that the issue was actually that the circa-2008 MicroSD card had failed. Documentation is updated and this PR is ready for review.