Zarf Getting started docs should include zarf-init download

[andrewg-xyz]

Include zarf-init.tar.zst download in https://github.com/defenseunicorns/zarf/tree/master/examples/game#get-ready

[btlghrants]

Just had a chat w/ @andrewsgreene about his experience & uncovered a couple nuggets that'll help us close out this issue:

• While the steps describing how to install a Zarf release (on the "Workstation Setup" page) do include "zarf-init.tar.zst", the way they're formatted is pretty poor--they're presented in such a way that the reader's eye just sort of skips over the "zarf-init.tar.zst". They need to be re-ordered / re-formatted to make the important bits stand out more.

• In addition to clarifying the install instructions, we should also add a note to the "Get Started" page's "Get Ready" step that mentions how multiple files are included as part of a Zarf release. This'll help prime the reader to see the tar.zst download instruction once they move over to the install instructions.

• It would also be worth adding a mention to the specific error received when a tar.zst is not found & how to fix it (i.e. have a tar.zst file) in the "Get Started" page's "Create a cluster" step. This would help catch download issues AND cases where someone did download the .tar.zst and just forgot to put it in the right folder.

[btlghrants]

I'm going to put some work in on this this morning under the umbrella of Issue #47 (same issue we put PR #124 "Get Started" example rewrite under).