Missing install instructions for QEMU

**Path to page with content (_do not_ include domain name):**

`/en/os/1.15.x/install/quickstart/`

**What content is incorrect?**

The current instructions only list AWS as environments where Bottlerocket can be installed, this leads people to believe that that's the only place you _can_ use Bottlerocket.

**What should the content say or communicate?**

For people who want to try it out, QEMU is an accessible and free starting point to get your hands on Bottlerocket.

Open the page at /en/os/1.15.x/install/quickstart/ and read the current installation-environment guidance. Update the page so it communicates that QEMU is an accessible, free option for trying Bottlerocket, and confirm the AWS-only impression is removed.

Written by the indexing model from the issue text.