docs(workflow-sharing): implement share-add command (reanahub#190)

Adds a new command to the CLI to share a workflow with a user.

Closes reanahub/reana-client#680

AUTHORS.md

@@ -6,6 +6,7 @@ The list of contributors in alphabetical order:
 - [Agisilaos Kounelis](https://orcid.org/0000-0001-9312-3189)
 - [Audrius Mecionis](https://orcid.org/0000-0002-3759-1663)
 - [Clemens Lange](https://orcid.org/0000-0002-3632-3157)
+- [Daan Rosendal](https://orcid.org/0000-0002-3447-9000)
 - [Diego Rodriguez](https://orcid.org/0000-0003-0649-2002)
 - [Domenic Gosein](https://orcid.org/0000-0002-1546-0435)
 - [Elena Gazzarrini](https://orcid.org/0000-0001-5772-5166)

docs/reference/reana-client-cli-api/index.md

@@ -37,6 +37,9 @@ Workflow execution commands:
  stop Stop a running workflow.
  validate Validate workflow specification file.
 
+Workflow sharing commands:
+ share-add Share a workflow with other users (read-only).
+
 Workspace interactive commands:
  close Close an interactive session.
  open Open an interactive session inside the workspace.
@@ -286,6 +289,23 @@ Examples:
 
   $ reana-client run -w myanalysis-test-big -p myparam=mybigvalue
 
+## Workflow sharing commands
+
+### share-add
+
+Share a workflow with other users (read-only).
+
+The `share-add` command allows sharing a workflow with other users. The
+users will be able to view the workflow but not modify it.
+
+Examples:
+
+<!-- markdownlint-disable no-bare-urls -->
+$ reana-client share-add -w myanalysis.42 --user [email protected]
+
+<!-- markdownlint-disable no-bare-urls -->
+$ reana-client share-add -w myanalysis.42 --user [email protected] --user [email protected] --message "Please review my analysis" --valid-until 2024-12-31
+
 ## Workspace interactive commands
 
 ### open