add docs

Author: wwwjn

docs/release.md

@@ -5,6 +5,7 @@ Currently we follow a lightweight release process.
     - if major features are added, increment `y`
     - if minor fixes are added, increment `z`
 - Create a new release at https://github.com/pytorch/torchtitan/releases/new
+  - In the tag section, create a new tag with the version number, e.g. `v0.y.z`. Choose the target branch as `main`.
   - In the release notes
     - include proper nightly versions for `torch` and `torchao`, which can be found in [latest CI](https://github.com/pytorch/torchtitan/actions/workflows/integration_test_8gpu.yaml) test log "Run script in container" section. E.g.
         - "Successfully installed ... `torch-2.8.0.dev20250605+cu126`"