Adds release/3.0.0-beta2 to docs (#5714)

# Description

Adds new release/3.0.0-beta2 to the docs for the QA cycle. This will be
the new release branch as we prepare for the Isaac Lab 3.0.0 Beta 2
release.

## Type of change

- Documentation update


## Checklist

- [x] I have read and understood the [contribution
guidelines](https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html)
- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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Author: kellyguo11

.github/workflows/docs.yaml

@@ -96,8 +96,9 @@ jobs:
         # "deploy" branches build the full set of versions so every page
         # has a complete version dropdown: main, develop, tags >= v2.0.0
         # (including pre-release suffixes like -beta or -rc1). v1.x tags and
-        # release/ branches are excluded.
-        SMV_BRANCH_WHITELIST: '^(main|develop)$'
+        # most release/ branches are excluded; release/3.0.0-beta2 is included
+        # explicitly to surface it in the version switcher.
+        SMV_BRANCH_WHITELIST: '^(main|develop|release/3\.0\.0-beta2)$'
         SMV_TAG_WHITELIST: '^v[2-9]\d*\.\d+\.\d+(-[A-Za-z0-9.]+)?$'
       run: |
         git fetch --prune --unshallow --tags

README.md

@@ -78,6 +78,7 @@ dependency versions for Isaac Sim.
 | ----------------------------- | ------------------------- |
 | `develop` branch              | Isaac Sim 6.0             |
 | `main` branch                 | Isaac Sim 4.5 / 5.0 / 5.1 |
+| `v3.0.0*`                     | Isaac Sim 6.0             |
 | `v2.3.X`                      | Isaac Sim 4.5 / 5.0 / 5.1 |
 | `v2.2.X`                      | Isaac Sim 4.5 / 5.0       |
 | `v2.1.X`                      | Isaac Sim 4.5             |