docs: add experimental mark for examples (#1569)

Signed-off-by: Billy Zha <[email protected]>

cmd/oras/root/attach.go

@@ -78,10 +78,10 @@ Example - Attach an artifact with manifest annotations:
 Example - Attach file 'hi.txt' and add manifest annotations:
   oras attach --artifact-type doc/example --annotation "key=val" localhost:5000/hello:v1 hi.txt
 
-Example - Attach file 'hi.txt' and format output in JSON:
+Example - [Experimental] Attach file 'hi.txt' and format output in JSON:
   oras attach --artifact-type doc/example localhost:5000/hello:v1 hi.txt --format json
 
-Example - Attach file 'hi.txt' and format output with Go template:
+Example - [Experimental] Attach file 'hi.txt' and format output with Go template:
   oras attach --artifact-type doc/example localhost:5000/hello:v1 hi.txt --format go-template --template "{{.digest}}"
 
 Example - Attach file 'hi.txt' and export the pushed manifest to 'manifest.json':

cmd/oras/root/discover.go

@@ -61,10 +61,10 @@ Example - Discover referrers via referrers API:
 Example - Discover referrers via tag scheme:
   oras discover --distribution-spec v1.1-referrers-tag localhost:5000/hello:v1
 
-Example - Discover referrers and display in a table view:
+Example - [Experimental] Discover referrers and display in a table view:
   oras discover localhost:5000/hello:v1 --format table
 
-Example - Discover referrers and format output with Go template:
+Example - [Experimental] Discover referrers and format output with Go template:
   oras discover localhost:5000/hello:v1 --format go-template --template "{{.manifests}}"
 
 Example - Discover all the referrers of manifest with annotations, displayed in a tree view:

cmd/oras/root/manifest/fetch.go

@@ -55,10 +55,10 @@ Example - Fetch raw manifest from a registry:
 Example - Fetch the descriptor of a manifest from a registry:
   oras manifest fetch --descriptor localhost:5000/hello:v1
 
-Example - Fetch the manifest digest from a registry similar to the resolve command:
+Example - [Experimental] Fetch the manifest digest from a registry similar to the resolve command:
   oras manifest fetch --format go-template --template '{{ .digest }}' localhost:5000/hello:v1
 
-Example - Fetch manifest and output metadata encoded in JSON:
+Example - [Experimental] Fetch manifest and output metadata encoded in JSON:
   oras manifest fetch localhost:5000/hello:v1 --format json
 
 Example - Fetch manifest from a registry with specified media type:

cmd/oras/root/pull.go

@@ -84,10 +84,10 @@ Example - Pull files from a registry with certain platform:
 Example - Pull all files with concurrency level tuned:
   oras pull --concurrency 6 localhost:5000/hello:v1
 
-Example - Pull files and format output in JSON:
+Example - [Experimental] Pull files and format output in JSON:
   oras pull localhost:5000/hello:v1 --format json
 
-Example - Pull files and format output with Go template:
+Example - [Experimental] Pull files and format output with Go template:
   oras pull localhost:5000/hello:v1 --format go-template="{{.reference}}"
 
 Example - Pull artifact files from an OCI image layout folder 'layout-dir':

cmd/oras/root/push.go

@@ -86,10 +86,10 @@ Example - Push file "hi.txt" with config type "application/vnd.me.config":
 Example - Push file "hi.txt" with the custom manifest config "config.json" of the custom media type "application/vnd.me.config":
   oras push --config config.json:application/vnd.me.config localhost:5000/hello:v1 hi.txt
 
-Example - Push file "hi.txt" and format output in JSON:
+Example - [Experimental] Push file "hi.txt" and format output in JSON:
   oras push localhost:5000/hello:v1 hi.txt --format json
 
-Example - Push file "hi.txt" and format output with Go template:
+Example - [Experimental] Push file "hi.txt" and format output with Go template:
   oras push localhost:5000/hello:v1 hi.txt --format go-template="{{.digest}}"
 
 Example - Push file to the insecure registry:
@@ -104,7 +104,7 @@ Example - Push repository with manifest annotations:
 Example - Push repository with manifest annotation file:
   oras push --annotation-file annotation.json localhost:5000/hello:v1
 
-Example - Push artifact to repository with platform:
+Example - [Experimental] Push artifact to repository with platform:
   oras push --artifact-platform linux/arm/v5 localhost:5000/hello:v1
 
 Example - Push file "hi.txt" with multiple tags: