The docker devcontainers are meant to be used by VSCode or in a Github Codespaces environment.
See the main README.md file in the ../.docker folder.
If you need to customize the values from devcontainer.json, you can copy it to a subfolder of .devcontainer.
Code will then ask you which file to use when starting the devcontainer.
I suggest the custom folder as it is already git-ignored but you can use any name.