[x] Add a way to modify the tree lines path object before drawing on the canvas (enabling line dashing/dotting).
The actual line dashing algorithm was not implemented in this PR, but the demo app was updated to include a visual example of the above using the path_drawing package.
[x] IndentGuide.padding
Optional inset values added to the padding that indents tree nodes and wraps TreeIndentation.child.
[x] Add an optional ┐ shaped line to ConnectingLinesGuide which connects parent and descendant lines.
IndentGuide.padding┐shaped line toConnectingLinesGuidewhich connects parent and descendant lines.Resolves #49