Explain ignore_* in license rule documentation

### Description

> A brief description of the Documentation Improvement or New Section request.

In the docs I can see:

```
Also attributes having ignorables in the license text:

- `ignorable_urls`
- `ignorable_copyrights`
- `ignorable_authors`
- `ignorable_holders`
- `ignorable_emails`
```
but these aren't explained. What do these mean? Are they used during matching or are they simply not reported (but matched)?

### Link to Documentation Page

> Where the confusion/inconsistency/incomplete documentation is.

### Select Category

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