Add tarball with git submodules similar to tarball with go mod vendor

### Description

The current Lima source tarball does **not** include the submodules:

```
[submodule "hack/bats/lib/bats-core"]
path = hack/bats/lib/bats-core
url = https://github.com/bats-core/bats-core.git
branch = master
[submodule "hack/bats/lib/bats-file"]
path = hack/bats/lib/bats-file
url = https://github.com/bats-core/bats-file.git
branch = master
[submodule "hack/bats/lib/bats-assert"]
path = hack/bats/lib/bats-assert
url = https://github.com/bats-core/bats-assert.git
branch = master
[submodule "hack/bats/lib/bats-support"]
path = hack/bats/lib/bats-support
url = https://github.com/bats-core/bats-support.git
branch = master
```

But we could export them to an "add-on" archive, on top of the other.

Like we are already doing with the go modules, in go-mod-vendor.tar.gz

Maybe also export `.gitmodules` and `git submodule status` to the archive?

Like we are including `go.mod` and `go.sum`, with the `vendor` archive.

Start by examining how go-mod-vendor.tar.gz is produced and how the current source tarball is assembled. Review the listed submodule paths, .gitmodules, and git submodule status to determine the archive contents. Done means an add-on archive includes the submodules and the intended metadata alongside the source tarball.

Written by the indexing model from the issue text.