It used to be the case that the entire superblock entry could be found
at specific offsets, but this was only possible while the superblock
entry was immutable. Now that the superblock entry is very mutable
(block-count changes, lfs2.0 -> lfs2.1 version bumps, etc), the correct
superblock entry may end up later in the metadata log.
At the very least, the "littlefs" magic string is still immutable and at
the specific offset offset=8. This is arguably the most useful
fixed-offset item.
See SPEC.md for more info.
Also considered adding an explanation to DESIGN.md, but there's not a
great place for it. Maybe FCRCs are too low-level for the high-level
design document. Though may be worth reconsidering if DESIGN.md gets
revisited.
Now with graphs! Images are stored on the branch gh-images in an effort
to avoid binary bloat in the git history.
Also spruced up SPEC.md and README.md and ran a spellechecker over the
documentation. Favorite typo so far was dependendent, which is, in fact,
not a word.
