Fix reference bindings missing in sdist

MANIFEST.in

@@ -12,6 +12,7 @@ recursive-include src/pypdfium2 *.py
 recursive-include setupsrc *.py
 recursive-include sourcebuild/patches *
 include autorelease/record.json
+include autorelease/bindings.py
 
 # By design, the raw module only ships data files - exclude them by default
 recursive-exclude src/pypdfium_raw *

docs/devel/changelog_staging.md

@@ -6,7 +6,7 @@
 # Changelog for next release
 - `PdfPage.get_objects()`: Don't register pageobjects as children, because they don't need to be closed by the caller when part of a page. This avoids excessive caching of weakrefs that are not cleaned up with the object they refer to.
 - Fixed another dotted filepath blunder in the `extract-images` CLI. (The `PdfImage.extract()` API is not affected this time.)
-- Fixed installation with reference bindings (`PDFIUM_BINDINGS=reference`) by adding a missing `mkdir` call. (In older versions, this can be worked around by unpacking the sdist and creating the missing directory manually before installation.)
+- Fixed installation with reference bindings (`PDFIUM_BINDINGS=reference`) by adding a missing `mkdir` call and actually including them in the sdist. (In older versions, this can be worked around by cloning the repository and creating the missing directory manually before installation.)
 - Fixed sourcebuild on windows by syncing patches with pdfium-binaries.
 - Updated test expectations: due to changes in pdfium, some numbers are now slightly different.
 - Fixed conda packaging: It is now required to explicitly specify `-c defaults` with `--override-channels`, presumably due to an upstream change.