Pass the text writing mode around in a new LayoutContext struct
Pass the text writing mode around in a new LayoutContext struct

We'll use this struct to hold the state of the SVG2 text layout
algorithm.  The writing-mode property of the <text> element is used
throughout the algorithm, so we keep it in a single place now.

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/621>

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg