[Testserver]4 in 1 issue ;-;

[dmgnr]

Describe the bug + feature

1. [FIXED IN BETA]The server.properties file is missing some(a lot) value because it is manually generated, it crash the server
2. Open unsupported file cause freeze
3. Make it automatically download a server-jar that match server-version set in the plugin's config
4. After you stop the server, you cannot start it again until you restart the program

To Reproduce
Steps to reproduce the behavior:
The #2
Just open a random file like server.jar ;-;

Desktop (please complete the following information):

• OS: Windows 10
• Browser Chrome
• Version Latest

Additional context
Umm I guess this is the best way to make a datapack

[dmgnr]

@MinimineLP First issue!!!
@Stevertus Yay