ci: add correct permissions for npm publishing (#946)

<!--- Provide a general summary of your changes in the Title above -->

## Description

<!--- Describe your changes in detail -->

## Related Issue(s)

- #{issue number}

## Verification

- [ ] **Your** code builds clean without any errors or warnings
- [ ] Manual testing done (required)
- [ ] Relevant automated test added (if you find this hard, leave it and
we'll help out)

## Documentation

- [ ] Documentation is updated (either in `docs`-directory, Altinnpedia
or a separate linked PR in
[altinn-studio-docs.](https://github.com/Altinn/altinn-studio-docs), if
applicable)

.github/workflows/action-publish-schema.yml

@@ -12,6 +12,9 @@ on:
 env:
   WORKING_DIRECTORY: docs/schema/V1
 
+permissions:
+  id-token: write
+
 jobs:
   publish-schema-to-npm:
     runs-on: ubuntu-latest