Set computed-prefix and version outputs

I've found these to be useful while composing this action with others.

README.md

@@ -44,6 +44,13 @@ Currently, changelog format and supported tag names have the following rule:
 | branch    | false    | Reject releases from commits not contained in branches that match the specified pattern (regular expression) | String  |         |
 | prefix    | false    | An optional pattern that matches a prefix for the release tag, before the version number (see [action.yml](action.yml) for more) | String |         |
 
+### Outputs
+
+| Name            | Description                                                                                                    |
+|-----------------|----------------------------------------------------------------------------------------------------------------|
+| computed-prefix | The computed prefix, including '-' and 'v'.                                                                    |
+| version         | The version number extracted from the tag. The tag name is a concatenation of `computed-prefix` and `version`.-|
+
 ### Example workflow: Basic usage
 
 ```yaml

action.yml

@@ -37,6 +37,14 @@ inputs:
     required: false
     default: ''
 
+outputs:
+  computed-prefix:
+    description: >
+      The computed prefix, including '-' and 'v' if found.
+  version:
+    description:
+      The version number extracted from the tag. The tag name is a concatenation of computed-prefix
+      and version.
 runs:
   using: node16
   main: main.js

main.sh

@@ -98,3 +98,8 @@ fi
 
 # https://cli.github.com/manual/gh_release_create
 gh release create ${draft_option:-} "${tag}" ${prerelease:-} --title "${title}" --notes "${notes:-}"
+
+# set (computed) prefix and version outputs for future step use
+computed_prefix=${tag%"$version"}
+echo "::set-output name=computed-prefix::${computed_prefix}"
+echo "::set-output name=version::${version}"