No documentation on calling ScanCode as a library

### Description

The ScanCode documentation mentions that it is possible to use it as a Python library, which is great when you want to use it from a Python script. It includes instructions to install it as a library: https://scancode-toolkit.readthedocs.io/en/stable/getting-started/install.html#installation-as-a-library-via-pip However, after that, there is zero documentation available on how to _use_ it as a library, making that choice not very practical.

Just a reference section on the Python API of ScanCode would already be a big improvement over digging through the source. Or, if you folks don't want to support that way of using it, then removing the section of the doc that lists that as a possibility would be a good idea. Thanks!

### Select Category

- [ ] Inconsistency
- [ ] New Section Request
- [x] General Improvement
- [ ] Typo/Mistakes
- [ ] Other