Add changelog

Author: cderv

news/changelog-1.9.md

@@ -29,6 +29,7 @@ All changes included in 1.9:
 - ([#13362](https://github.com/quarto-dev/quarto-cli/issues/13362)): Remove unused `blockquote` definitions from template.
 - ([#13452](https://github.com/quarto-dev/quarto-cli/issues/13452)): Wraps subfigure captions generated by `quarto_super()` in `block` function to avoid emitting `par` elements. (author: @christopherkenny)
 - ([#13474](https://github.com/quarto-dev/quarto-cli/issues/13474)): Heading font for title should default to `mainfont`.
+- ([#13589](https://github.com/quarto-dev/quarto-cli/issues/13589)): Fix callouts with invalid ID prefixes crashing with "attempt to index a nil value". Callouts with unknown reference types now render as non-crossreferenceable callouts with a warning, ignoring the invalid ID.
 
 ## Projects