Summary:
## Changes in this pull request
### Checklist
- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Pull Request resolved: https://github.com/Instagram/IGListKit/pull/1453
Reviewed By: lorixx
Differential Revision: D23836038
Pulled By: joetam
fbshipit-source-id: 8245415992a5b1ed49f67ebfcf9f85a2745a8042
Summary:
**Changes occurred only for the IGListCollectionViewLayout.**
**Specifically:**
1. Harnessed the hardcore to the fact that it is possible to use only headers.
2. Assertions removed
3. Caching for layout of attributes of footers
4. Implemented the location of the footers in any orientation scroll
Issue fixed: #898
I need this enhancement ASAP 🙏
**Example:**
Footers with user comments count
- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
- [x] I updated example project with implemented feature
Closes https://github.com/Instagram/IGListKit/pull/1017
Reviewed By: jeremycohen
Differential Revision: D6385893
Pulled By: rnystrom
fbshipit-source-id: 5f1bad5655d2df321f8c71496aa797ac8e3d226a
