ci: add the permission to release assets (#160)

The release v1.7.0 failed due to the permission error.

https://github.com/Boeing/config-file-validator/actions/runs/10362649156/job/28684983356#step:6:284

```
+ github-assets-uploader -logtostderr -f ../validator-v1.7.0-linux-amd64.tar.gz -mediatype application/gzip -repo Boeing/config-file-validator -token *** -tag=v1.7.0 -releasename= -retry 3
W0813 02:34:38.260789    1654 main.go:48] Upload asset error, will retry in 4s: POST https://uploads.github.com/repos/Boeing/config-file-validator/releases/169879682/assets?name=validator-v1.7.0-linux-amd64.tar.gz: 403 Resource not accessible by integration []
W0813 02:34:42.775738    1654 main.go:48] Upload asset error, will retry in 9s: POST https://uploads.github.com/repos/Boeing/config-file-validator/releases/169879682/assets?name=validator-v1.7.0-linux-amd64.tar.gz: 403 Resource not accessible by integration []
E0813 02:34:52.242572    1654 err_exit.go:11] POST https://uploads.github.com/repos/Boeing/config-file-validator/releases/169879682/assets?name=validator-v1.7.0-linux-amd64.tar.gz: 403 Resource not accessible by integration []
```

The permission `contents: write` is required, but it was removed by f28a04d#diff-87db21a973eed4fef5f32b267aa60fcee5cbdf03c67fafdc2a9b553bb0b15f34 .
So this commit adds the permission.

.github/workflows/release.yml

@@ -27,6 +27,7 @@ jobs:
 
     permissions:
       packages: write
+      contents: write
 
     steps:
     - name: Harden Runner