Jupyterlab-h5web

* Fix HDF path join on Windows 56

- Prevent HDF5 file content fetching when opening in the file browser (patch of https://github.com/silx-kit/jupyterlab-h5web/issues/24)

- Updated h5web to [0.0.27](https://github.com/silx-kit/h5web/releases/tag/v0.0.27)
- Fixes 45
- Improves the behaviour of the h5web notebook cell for long filenames 47

- Now using `jupyterlab_h5web` instead of `jupyterlab_hdf` to serve HDF5 files contents. This fixes the following issues:
- The path given to `H5Web` widget is now resolved relatively to the working directory and can be absolute 37
- Add support for external links 39
- Handle base directory correctly for JupyterLab 3.x 41
- Updated h5web to [0.0.24](https://github.com/silx-kit/h5web/releases/tag/v0.0.24)
- Changed dark mode implementation 32

h5web can be used in notebooks :notebook: ! :tada:
[Demo available on Binder !](https://mybinder.org/v2/gh/silx-kit/jupyterlab-h5web/HEAD?urlpath=lab/tree/example.ipynb)


Release notes

- Updated `h5web/app` to [0.0.14](https://github.com/silx-kit/h5web/releases/tag/v0.0.14)
- Added `H5Web` notebook widget to `jupyterlab_h5web` Python package