Pycfmodel

Fixes
- Fix model for IAM Role which was missing `Description` and `Tags`.
- Fix README.md tabs on list of available models.
Updates
- Update `CLOUDFORMATION_ACTIONS`.
- Updated tests accordingly for IAM Role

Fixes
- Fix docs that were failing to get updated/generated
Improvements
- Add tests for docs so they don't get outdated
Updates
- Update `CLOUDFORMATION_ACTIONS`.

Additions
- New `RDSDBSecurityGroup` and `RDSDBSecurityGroupIngress` resources [103]
Improvements
- IAM Role is able to return its `AssumeRolePolicyDocument` as a list of `OptionallyNamedPolicyDocument`. [102](https://github.com/Skyscanner/pycfmodel/pull/102)
Updates
- Compatible with Python3.10 [100](https://github.com/Skyscanner/pycfmodel/pull/100)
- Update `CLOUDFORMATION_ACTIONS`.

Fixes
- `Effect` on `Statement` is **required**. [101](https://github.com/Skyscanner/pycfmodel/pull/97)
Updates
- Update `CLOUDFORMATION_ACTIONS`.

Improvements
- Able to parse PolicyDocument that are implicit in string properties. [97](https://github.com/Skyscanner/pycfmodel/pull/97)

Fixes
- Fix obtaining `policy_documents` for resources without properties. [98](https://github.com/Skyscanner/pycfmodel/pull/96)
Updates
- Update `CLOUDFORMATION_ACTIONS`.