[Copilot] investigate the new code generation instructions on VSCode

[martinlippert]

https://code.visualstudio.com/updates/v1_93#_code-generation-instructions

You can have code generation instructions now in VSCode, which looks like a similar concept that we are adopting with the pre-defined prompts to tell Copilot Spring- and/or project specific things. Probably worth to look into the new feature of VSCode to see how we can benefit from that.