chore: unpack spring boot executable jar before run and update docs

[vmutafov]

No description provided.

[ThuF]

@vmutafov I guess this would affect how "Custom Stacks" are created, for example:

• https://github.com/codbex/codbex-kronos/blob/main/application/Dockerfile
• https://github.com/codbex/codbex-atlas/blob/main/application/Dockerfile
• https://github.com/codbex/codbex-helios/blob/main/application/Dockerfile

[vmutafov]

@ThuF yes, you're right, but I plan to add a Dockerfile.base that would create a base image where we have all our dependency tools like esbuild, tsc, etc., and have this base image used where necessary. I'll convert this PR to a draft one for now