fix: correct typos found by codespell

Fix various typos across source code, tests, and documentation:
- README.md: Preforming → Performing
- pull.go: commpleted → completed
- server_test.go: unxpected → unexpected
- diff.go: atleast → at least
- content.go: desciptor → descriptor
- remote.go: requst → request
- imagestore_test.go: expeceted → expected
- pull_test.go: shoule → should

Signed-off-by: majianhan <majianhan@kylinos.cn>

core/diff/diff.go

@@ -138,7 +138,7 @@ func WithSyncFs(sync bool) ApplyOpt {
 }
 
 // WithProgress is used to indicate process of the apply operation, should
-// atleast expect a progress of 0 and of the final size. It is up to the applier
+// at least expect a progress of 0 and of the final size. It is up to the applier
 // how much progress it reports in between.
 func WithProgress(f func(ocispec.Descriptor, int64)) ApplyOpt {
 	return func(_ context.Context, desc ocispec.Descriptor, c *ApplyConfig) error {