Bump version to 0.5.0 (#74)
Version 0.5.0 includes the following changes:
* Add support for binding multiple attributes at once
* Add DomRenderer for rendering to the web (with the help of pyscript)
* Add support for text elements (currently only supported by DomRenderer and DictRenderer)
* Add support in CGX for formatting text of text elements with moustaches: {{ <python expression> }}
* Drop Python 3.8 support
* Small CGX render function optimization by removing empty list comprehensions
* Fix for lambda arguments in event handlers
* Fix for referencing scope outside of component class in CGX files
* Prevent overwriting the `state` and `props` attributes on component
* PySide renderer:
* Improve configuration of dialog button box buttons
* Add support for: QDockWidget, QStatusBar, QToolBar
* Make it possible to remove (custom) attributes (needed for reuse of widgets)
* Add basic support for setting items of QComboBox
* Pygfx renderer:
* Make it possible to remove (custom) attributes (needed for reuse of objects)
