Document how to fix 'Reasource not Available by Integration'

Related issue: https://github.com/game-ci/unity-test-runner/issues/249

> Reasource not Available by Integration

This message is related to the following StackOverflow:
https://stackoverflow.com/questions/70435286/resource-not-accessible-by-integration-on-github-post-repos-owner-repo-ac

This happens because the pipeline doesn't have the right to publish the report for the tests.

Option 1: Go in **project's settings > Workflow Permissions section** and _give actions Read and Write permissions_.
Option 2: explicitly add the required permissions to the job using this action, e.g.:

```yaml
jobs:
test:
permissions:
checks: write
...
steps:
- name: Run Tests
uses: game-ci/unity-test-runner@v4
```

source: https://github.com/game-ci/unity-test-runner/issues/249#issuecomment-1856067967

1. Identify all example snippets in our docs that would benefit from the `permissions`. Can be done by searching for "game-ci/unity-test-runner" in the code (yaml snippets).
2. Update the examples with the permissions check
3. Document the error, the fix and the permission check somewhere.

The last thing I would like to validate: if we have the `permissions` checks in the yaml, I suppose we still have to _give actions Read and Write permissions_, is that right?