Rocrate

* [Fix entity getitem when value is None (JSON null)](https://github.com/ResearchObject/ro-crate-py/pull/102)

* [Fixed container data model implementation for Entity](https://github.com/ResearchObject/ro-crate-py/pull/87)
* [Fixed errors when updating an existing RO-Crate](https://github.com/ResearchObject/ro-crate-py/issues/86)
* [Fixed dataset writing when source is a string](https://github.com/ResearchObject/ro-crate-py/pull/93)
* [Fixed duplicate metadata entry for preview when writing a crate](https://github.com/ResearchObject/ro-crate-py/pull/95)
* [Added support for COMPSs as computer language](https://github.com/ResearchObject/ro-crate-py/pull/96/files)
* [Fixed reading errors with recent crates from WorkflowHub](https://github.com/ResearchObject/ro-crate-py/pull/100)

* [Added contributing guide](https://github.com/ResearchObject/ro-crate-py/pull/59)
* [Initial support for entity deletion](https://github.com/ResearchObject/ro-crate-py/pull/65)
* [Added write-zip command to the CLI](https://github.com/ResearchObject/ro-crate-py/pull/67)
* [Added CITATION.cff](https://github.com/ResearchObject/ro-crate-py/pull/71)
* [Data entities handling improvements](https://github.com/ResearchObject/ro-crate-py/pull/85)
* Support for remote datasets
* Support for BytesIO file source
* UTC datetime formatting
* Several minor tweaks
* Support for [missing files and directories](https://github.com/ResearchObject/ro-crate-py/pull/75) and [unknown data entities](https://github.com/ResearchObject/ro-crate-py/pull/76)
* Bug fixes and performance improvements

* [Methods to add test-related entities](https://github.com/ResearchObject/ro-crate-py/pull/43)
* ["init" mode and first version of a CLI tool](https://github.com/ResearchObject/ro-crate-py/pull/46)
* [Support referring to test suites from the root dataset](https://github.com/ResearchObject/ro-crate-py/pull/55)
* various fixes

Fix requirements list

Adds support for [workflow testing metadata](https://github.com/crs4/life_monitor/wiki/Workflow-Testing-RO-Crate).