update documentation

Signed-off-by: kubasobon <[email protected]>

docs/skopeo-sync.1.md

@@ -215,6 +215,10 @@ registry.example.com:
             - "sha256:0000000000000000000000000000000011111111111111111111111111111111"
     images-by-tag-regex:
         nginx: ^1\.13\.[12]-alpine-perl$
+    images-by-semver:
+        alpine:
+            - "3.12 - 3.13"
+            - ">= 3.17"
     credentials:
         username: john
         password: this is a secret
@@ -235,6 +239,7 @@ This will copy the following images:
 - Repository `registry.example.com/redis`: images tagged "1.0" and "2.0" along with image with digest "sha256:0000000000000000000000000000000011111111111111111111111111111111".
 - Repository `registry.example.com/nginx`: images tagged "1.13.1-alpine-perl" and "1.13.2-alpine-perl".
 - Repository `quay.io/coreos/etcd`: images tagged "latest".
+- Repository `registry.example.com/alpine`: all images with tags satisfying either "3.12 - 3.13" condition ("3.12.0", "3.12.1"...) or ">= 3.17" ("3.17.5", "3.19.0", "4.0.0"...)
 
 For the registry `registry.example.com`, the "john"/"this is a secret" credentials are used, with server TLS certificates located at `/home/john/certs`.