Null-safety support

[2.0.0]

*** Breaking Changes ***

Stable null-safety support.

Horizontal timeline support

[1.0.0]

*** Breaking Changes ***

API changes to support both vertical and horizontal timeline.

1. TimelineAlign changes:

• TimelineAlign.left renamed to TimelineAlign.start
• TimelineAlign.right renamed to TimelineAlign.end

2. Added TimelineAxis to control the axis.

3. TimelineTile changes:

• new parameter TimelineAxis axis
• rightChild renamed to endChild
• leftChild renamed to startChild
• lineX renamed to lineXY
• topLineStyle renamed to beforeLineStyle
• bottomLineStyle renamed to afterLineStyle

4. LineStyle changes:

• width renamed to thickness

5. IndicatorStyle changes:

• indicatorY renamed to indicatorXY

6. TimelineDivider changes:

• added parameter axis to support both axis

Release 0.1.2

Fixed example 8 assets

Initial release

First project release published to pub.dev