Update app.json

[Samukaii]

It would be interesting if by clicking on the button to deploy, the user could choose the version of minecraft

[jkutner]

I'm worried that this change will give the impression that any version is allowed here. But really we only allow certain (usually the latest) of a particular minor version (like 1.16.2, but not 1.16.1).

Before we merge something like this, I think we would need to update the code here so that it allows for any version.
https://github.com/jkutner/heroku-buildpack-minecraft/blob/master/bin/compile#L65-L79

One way we could do this is by creating a files.json in the repo with a mapping of "version" -> "sha" or something, like:

[
  {
    "minecraft": [
      {"version": "1.16.2", "uuid": "a412fd69db1f81db3f511c1463fd304675244077"},
      {"version": "1.15.2", "uuid": "bb2b6b1aefcd70dfd1892149ac3a215f6c636b07"}
    ]
  }
]

Then we could read that file in the bin/compile. I'll take a look at this later in the week.