Release v1.6.0

Highlights:
- A new sif: transport
- New options --multi-arch, --preserve-digests, --sign-passphrase-file

- Use a dynamic temp dir for test
- Add an option to allow copying image indexes alone
- proxy: Add a GetFullConfig method
- proxy: Also bump compatible semver
- Add option to preserve digests on copy
- Run codespell on code
- prompt-less signing via passphrase file
- add a SIF systemtest
- Merge pull request #1550 from vrothberg/sif-test
- Improve the documentation of the argument to (skopeo inspect)
- Document where various fields of (skopeo inspect) come from
- Improve the documentation of boolean flags

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

version/version.go

@@ -1,4 +1,4 @@
 package version
 
 // Version is the version of the build.
-const Version = "1.5.3-dev"
+const Version = "1.6.0"