✨ Add support for package requiring itself, add extras to --tree --json

[ddelange]

Fixes #95

Only triggers cyclic mechanic when the package requires the same extra as its ancestor (not the case here):

$ pipgrip --tree etils[etree,epath]
etils[epath,etree] (0.9.0)
├── etils[array_types] (0.9.0)
├── etils[enp] (0.9.0)
│   ├── etils[epy] (0.9.0)
│   │   └── typing-extensions (4.4.0)
│   └── numpy (1.23.5)
├── etils[epy] (0.9.0)
│   └── typing-extensions (4.4.0)
├── etils[etqdm] (0.9.0)
│   ├── absl-py (1.3.0)
│   ├── etils[epy] (0.9.0)
│   │   └── typing-extensions (4.4.0)
│   └── tqdm (4.64.1)
├── importlib-resources (5.10.0)
├── typing-extensions (4.4.0)
└── zipp (3.10.0)

[github-actions]

Released 0.9.0