doc - update multi source include description

Co-authored-by: Jed Brown <[email protected]>

doc/sphinx/source/releasenotes.md

@@ -22,7 +22,7 @@ for each release of libCEED.
 
 - `CeedScalar` can now be set as `float` or `double` at compile time.
 - Added JiT utilities in `ceed/jit-tools.h` to reduce duplicated code in GPU backends.
-- Added support for JiT of QFunctions with `#include` statements for additional local files.
+- Added support for JiT of QFunctions with `#include "relative/path/local-file.h"` statements for additional local files. Note that files included with `""` are searched relative to the current file first, then by compiler paths (as with `<>` includes). To use this feature, one should adhere to relative paths only, not compiler flags like `-I`, which the JiT will not be aware of.
 - Remove need to guard library headers in QFunction source for code generation backends.
 
 ### Maintainability