Add changelog

Author: fangerer

docs/changelog.rst

@@ -1,15 +1,28 @@
 Changelog
 =========
 
-Version 0.0.3 (September ??, 2021)
+Version 0.0.3 (September 22nd, 2021)
 ----------------------------------
 
-XXX Short one paragraph description of release and highlights XXX
+This release adds various new API functions (see below) and extends the debug 
+mode with the ability to track closed handles.
+The default ABI mode now is 'universal' for non-CPython implementations.
+Also, the type definition of `HPyContext` was changed and it's no longer a
+pointer type.
+The name of the HPy dev package was changed to 'hpy' (formerly: 'hpy.devel').
+Macro HPy_CAST was replaced by HPy_AsStruct.
 
 New features:
 
-- XXX
+  - Added helper HPyHelpers_AddType for creating new types
+  - Support format specifier 's' in HPyArg_Parse
+  - Added API functions: HPy_Is, HPy_AsStructLegacy (for legacy types),
+    HPyBytes_FromStringAndSize, HPyErr_NewException, HPyErr_NewExceptionWithDoc,
+    HPyUnicode_AsUTF8AndSize, HPyUnicode_DecodeFSDefault, HPyImport_ImportModule
+  - Debug mode: Implemented tracking of closed handles
+  - Debug mode: Add hook for invalid handle access
 
 Bug fixes:
 
-- XXX
+  - Distinguish between pure and legacy types
+  - Fix Sphinx doc errors