What's Changed
* Use None to access non-dictionary data by gerlero in https://github.com/gerlero/foamlib/pull/154
* Rename FoamDict to FoamFileBase by gerlero in https://github.com/gerlero/foamlib/pull/155
* Make FoamFileIO private by gerlero in https://github.com/gerlero/foamlib/pull/156
* Hide FoamFile header from __iter__ by gerlero in https://github.com/gerlero/foamlib/pull/157
* Remove FoamFile.Header class by gerlero in https://github.com/gerlero/foamlib/pull/158
* Add create method to FoamFile by gerlero in https://github.com/gerlero/foamlib/pull/159
* Add __delitem__ methods by gerlero in https://github.com/gerlero/foamlib/pull/160
* Fix AsyncFoamCase cpus handling by gerlero in https://github.com/gerlero/foamlib/pull/161
* Update pytest-asyncio requirement from <0.24,>=0.21 to >=0.21,<0.25 by dependabot in https://github.com/gerlero/foamlib/pull/162
* Improve serialization by gerlero in https://github.com/gerlero/foamlib/pull/163
* Improve serialization by gerlero in https://github.com/gerlero/foamlib/pull/164
* Improve serialization by gerlero in https://github.com/gerlero/foamlib/pull/165
**Full Changelog**: https://github.com/gerlero/foamlib/compare/v0.3.21...v0.4.0