[Docs] Release notes and link to contribution docs

Flesh out this project to conform to the style of other projects in
the OpenAssetIO org, in preparation for a release. A release will give
us a tag that can be used to link OpenAssetIO version to associated
compatible OpenAssetIO-Test-CMake version.

Signed-off-by: David Feltell <david.feltell@foundry.com>

Author: feltech

README.md

@@ -46,3 +46,8 @@ repository for more information.
 > Python test targets are currently unsupported in this mode. If
 > `OPENASSETIOTEST_ENABLE_PYTHON` is `ON` (default) then CMake will fail
 > to configure with an error.
+
+## Development notes
+
+This package follows the main
+[OpenAssetIO contribution process](https://github.com/OpenAssetIO/OpenAssetIO/blob/main/contributing/PROCESS.md).

RELEASE_NOTES.md

@@ -0,0 +1,9 @@
+Release Notes
+=============
+
+vX.X.X
+--------------
+
+### New Features
+
+* Initial version testing OpenAssetIO 1.0.0-alpha.6.