Installation instructions in README does not work

This instruction in current README.md

```
# Reference a semver major version only (GitHub recommended)
- uses: asdf-vm/actions/install@v4
```
When I try this, I get the following error:
```
Error: Unable to resolve action `asdf-vm/actions@v4`, unable to find version `v4`
```
I checked, there is no `v4` tag in the repo, maybe this is the issue.

Open README.md and inspect the installation example that uses asdf-vm/actions/install@v4. Compare that reference with the action repository's available tags, update the documentation to use a resolvable version, and verify the example no longer requests the missing v4 tag.

Written by the indexing model from the issue text.