support pyproject.toml as dependency system in `dlt init`

[djudjuu]

Feature description

if i run dlt init and I already have a requirements.txt file or a pyproject.toml file, any new requirements should be added to the respective file, if the requirement is not already there. in case it is just print it out and let the user should resolve it manually

Note: this shall be compatible with dlt+ project cli, which may call dlt source <newSource> add kafka or dlt run project init kafka postgres in which case 'dlt[postgres]>=0.5.1' and confluent-kafka>=2.3.0

should be added to pyproject.toml (if the project is in package-layout) and to requirements.txt if its in flat-layout

Are you a dlt user?

None

Use case

make dlt+ project more userfriendly

Proposed solution

dlt.cli.init_command.py.init_command()

Related issues

came up while doing this: https://github.com/dlt-hub/dlt/pull/2501