Use graphql api to determine linked issues (#14)

* Compile

* Use Graphql to get linkedissues

* Remove mention of limitation from README

---------

Co-authored-by: Ronald van Rij <ronald.rij@logius.nl>
Co-authored-by: Ronald van Rij <ronaldvanrij@users.noreply.github.com>

Author: michalvankodev

README.md

@@ -1,10 +1,10 @@
 # copy-issue-labels github action
 
-Motivation for creating this action was to copy labels from linked issues to the issue / PR which triggered workflow.
+Motivation for creating this action was to copy labels from linked issues to the issue / PR which triggered the workflow.
 
 ## Example workflow
 
-This workflow will copy labels from the linked issue for the opened PR.
+This workflow will copy labels from any linked issue for the opened PR.
 
 Github issues can link other issues and this linking is done automatically whenever PR mentions one of the keywords for automated workflows. [See documentation](https://docs.github.com/en/free-pro-team@latest/github/managing-your-work-on-github/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword)
 
@@ -35,8 +35,6 @@ There is also support for different workflows to trigger sync of the labels with
           issue-number: ${{ github.event.inputs.issue }}
 ```
 
-Because GitHub API doesn't provide information about linked issues this workflow will parse the information from the `body` of the issue.
-
 ## Custom keywords
 
 You can provide custom keywords which will be picked up by the parser.

action.yml

@@ -11,6 +11,9 @@ inputs:
   from-title:
     description: 'To parse the issue numbers from title, a boolean'
     required: false
+  issue-number:
+    description: 'Get linked issues from Pull Request number'
+    required: false
 runs:
-  using: 'node12'
+  using: 'node16'
   main: 'dist/index.js'