Diff-pdf-visually

- feat: add a `--version` command line argument (dc0ddf5acf)

Fixes

- restore the entry point, so that you can run again from the command line (1bde4171ab5970c42dcec353b9052eb37ca0996c)

Fixes

* Polyfill nullcontext to restore compatibility with py3.6. (95155617)
* Document compatibility with Python versions. (95155617)
* Correct URL in setup.py (3342f11a)

Fixes

* build: restore declared compatibility with py36, py37; fix tox config instead

Features

* New 'tempdir' argument to pdfdiff_pages, to specify a directory in which temporary images & image difference will be kept (f72bb560)