Add __version__ attribute to ninetoothed package

[stever178]

pytest output:

=========================== test session starts ============================
platform linux -- Python 3.12.3, pytest-9.0.1, pluggy-1.6.0
rootdir: /home/vipuser/projects/ninetoothed
configfile: pyproject.toml
plugins: anyio-4.11.0, cov-7.0.0
collected 127 items

tests/test_add.py .                                                  [  0%]
tests/test_addmm.py ..                                               [  2%]
tests/test_aot.py .....                                              [  6%]
tests/test_attention.py ........                                     [ 12%]
tests/test_conv2d.py .                                               [ 13%]
tests/test_data_ptr.py .                                             [ 14%]
tests/test_debugging.py .                                            [ 14%]
tests/test_dropout.py .                                              [ 15%]
tests/test_eval.py ........                                          [ 22%]
tests/test_expand.py .                                               [ 22%]
tests/test_generation.py ........................................... [ 56%]
................................                                     [ 81%]
tests/test_ipynb.py .                                                [ 82%]
tests/test_jagged.py ........                                        [ 88%]
tests/test_matmul.py ..                                              [ 90%]
tests/test_max_pool2d.py ..                                          [ 92%]
tests/test_naming.py .......                                         [ 97%]
tests/test_pow.py .                                                  [ 98%]
tests/test_softmax.py .                                              [ 99%]
tests/test_unsqueeze.py .                                            [100%]

===================== 127 passed in 202.58s (0:03:22) ======================

[voltjia]

还需要再考虑一下怎么加 __version__ 比较好，要是单纯依赖 importlib.metadata.version 的话，如果是 pip install -e .，使用的版本可能与安装显示的不同，而如果 hard-code 的话，那每次版本迭代还需要特地来这里改一下。

[stever178]

那么可否用 hatch 自带的版本管理，这样也能让版本号只写在一个文件里。