Create: Astral V2.1.3 version bump + misc. changes

[kumail-r]

Hello!

I've done a few things in this PR, so feel free to ask me to separate them out into different ones so that you can pick and choose some of the changes in particular. Let me know!

Here's what I've done:

• Updated Dockerfile to download the latest version of the Create: Astral server pack. I changed the file ID from 5864156 to 6057416.
  • Old: https://www.curseforge.com/api/v1/mods/681792/files/5864156
  • New: https://www.curseforge.com/api/v1/mods/681792/files/6057416
• I've updated all the references I could find of the container image since its path appears to have changed due to a name change by @claraphyll (let me know if I'm mistaken).
• I updated README.md to reference the most recent version of Create: Astral.
• I've also added some information to README.md about how people can build the container themselves using compose rather than download it from the container registry. I also added a brief explanation about how people can use this to modify things like the JVM arguments.
  • Some of the context behind why I added this to the README is because I was confused why the container wasn't starting up for me, and the reason ended up being because the machine I was attempting it on couldn't free 6gb of memory to allocate to the JVM. I needed to modify entrypoint.sh to slightly reduce the amount of memory allocated (and it worked).
  • It may be worth considering adding an environment variable to compose.yaml to allow for easier control over the amount of memory the user wants to allocate to the server.

[claraphyll]

lgtm, sorry for letting this sit for so long