Prepare release v0.13.0 (#239)

## heroku/python

### Changed

- Stopped manually creating a `src` directory inside the Pip dependencies layer. Pip will create the directory itself if needed (when there are editable VCS dependencies). ([#228](#228))
- Stopped setting `CPATH` and `PKG_CONFIG_PATH` at launch time. ([#231](#231))
- The `bin` directory in the Pip dependencies layer is now always added to `PATH` instead of only when an installed dependency has an entry point script. ([#232](#232))
- The Pip cache layer is now exposed to Pip invocations in later buildpacks. ([#234](#234))

Co-authored-by: heroku-linguist[bot] <136119646+heroku-linguist[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.13.0] - 2024-08-01
+
 ### Changed
 
 - Stopped manually creating a `src` directory inside the Pip dependencies layer. Pip will create the directory itself if needed (when there are editable VCS dependencies). ([#228](https://github.com/heroku/buildpacks-python/pull/228))
@@ -167,7 +169,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Initial implementation. ([#3](https://github.com/heroku/buildpacks-python/pull/3))
 
-[unreleased]: https://github.com/heroku/buildpacks-python/compare/v0.12.1...HEAD
+[unreleased]: https://github.com/heroku/buildpacks-python/compare/v0.13.0...HEAD
+[0.13.0]: https://github.com/heroku/buildpacks-python/compare/v0.12.1...v0.13.0
 [0.12.1]: https://github.com/heroku/buildpacks-python/compare/v0.12.0...v0.12.1
 [0.12.0]: https://github.com/heroku/buildpacks-python/compare/v0.11.0...v0.12.0
 [0.11.0]: https://github.com/heroku/buildpacks-python/compare/v0.10.0...v0.11.0

buildpack.toml

@@ -2,7 +2,7 @@ api = "0.10"
 
 [buildpack]
 id = "heroku/python"
-version = "0.12.1"
+version = "0.13.0"
 name = "Heroku Python"
 homepage = "https://github.com/heroku/buildpacks-python"
 description = "Heroku's buildpack for Python applications."