Version 2.50.0

- The following is a summary of changes between 2.48.x and 2.50.0.  For
  full details, please see the 2.49.x release notes below.

- This release requires at least Rust 1.40.

- Windows builds now support ARM64, thanks to Chun-wei Fan.

- Librsvg now consumes much less memory for large SVG files.  The limit for
  the maximum number of elements in an SVG is bigger now at 1 million
  elements (this limit exists to avoid unbounded memory consumption by
  maliciously large files, and is plenty to render even very detailed
  maps).  Thanks to Sergey "Shnatsel" Davidoff and Adam Reichold for making
  this possible.

- #34 - The 'font' shorthand in is now supported in CSS.  Librsvg
  ignores the 'line-height' sub-property because it cannot be done
  easily with Pango, but everything else in 'font' should work now.

- Many new features from SVG2:

- #508 - radialGradient now supports the "fr" property from SVG2
  (Dunja Lalic, Corentin Rossignon).

- #568 - Support href attribute in addition to xlink:href per SVG2.

- #560 - Ignore missing filter references per SVG2.

- #607 - Support the mix-blend-mode property from SVG2 and the
  Compositing and Blending Level 1 specification, so layers can be
  composited with operators like multiply/screen/color-burn, etc.
  https://www.w3.org/TR/compositing-1/ (John Ledbetter).

- #473 - Support the paint-order property from SVG2, so one can pick
  the order in which a path's fill/stroke/markers are drawn (John Ledbetter).

- Many bug fixes and little optimizations; see the 2.49.x release notes for
  details.  Thanks to Paolo Borelli, Daniel Kolesa, Ernestas Kulik.
  Sven Neumann, Bastien Orivel, Jordan Petridis, Emile Snyder.

- Special thanks to Sven Neumann for fixing all the cargo-clippy lints.