Rewrite Creating Custom egg and Docker image

[QuintenQVD0]

This PR is not perfect I do know that.

But changes in this pr

• mention how the pterodactyl install proces works (with the /mnt/server and /home/container)
• mention that no files can be in the docker container
• give an example on how to use the file parser
• mention how to use variables in the file parser
• mention how to set multiple done lines
• change the the java 17 example dockerfile and entrypoint
• mention that we now mosty use debian based image and not alpine anymore
• mention the requirement of the package iproute2 for the ip command

[QuintenQVD0]

I have no idea wy the github build faild

[Jcodeerd]

A few typos and improvements

[QuintenQVD0]

I found the issue, you can not without a code block use {{}}

So now I just made it look like this, what to be honest is still pritty good

[QuintenQVD0]

Please hold off on merging this, I am going to add an egg featured section and explain some more on validation of egg variables. So that it meets #434

[danny6167]

Thank you for all the work done on this so far.
I don't know if you plan to complete it or not, but as you've indicated that it's not ready to merge I'm converting it to a draft PR.