* Configure Cirrus CI
* Read file directly instead of shelling a command
* Wait for all streams to finish
* Add LTR `textDirection`
Since `RenderFlex#_debugHasNecessaryDirections` requires it when `direction` is horizontal and there are multiple children.
Now we just have one TextSpan class that handles both simple strings, trees of
children, and styling both. This approach simplifies the interface for most
clients.
This patch also removes StyledText, which was weakly typed and tricky to use
correctly. The replacement is RichText, which is strongly typed and uses
TextSpan.
