Initial release. The API follows auto_size_text 3.0.0, with these changes:

• textScaler replaces textScaleFactor. The fitted font size accounts for the ambient MediaQuery scaler, including nonlinear scalers.
• Rich text is measured with the fully resolved style, matching how Text.rich renders it.
• Measurement resolves textAlign and textDirection like the rendered Text instead of assuming left-aligned, left-to-right text.
• A single TextPainter is reused for all fit measurements of a widget.
• textWidthBasis, textHeightBehavior and selectionColor are passed through to the built Text.
• presetFontSizes are asserted to be in descending order.