Prepare release v0.1.8 (#138)

## heroku/go

- Ensure $GOROOT/go.env is installed.
- Added go1.21.0.

Co-authored-by: joshwlewis <[email protected]>

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.1.8] - 2023-08-15
+
 - Ensure $GOROOT/go.env is installed.
 - Added go1.21.0.
 
@@ -46,12 +48,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Initial implementation using libcnb.rs ([#1](https://github.com/heroku/buildpacks-go/pull/1))
 
-[unreleased]: https://github.com/heroku/buildpacks-go/compare/v0.1.7...HEAD
+[unreleased]: https://github.com/heroku/buildpacks-go/compare/v0.1.8...HEAD
+[0.1.8]: https://github.com/heroku/buildpacks-go/compare/v0.1.7...v0.1.8
 [0.1.7]: https://github.com/heroku/buildpacks-go/compare/v0.1.6...v0.1.7
 [0.1.6]: https://github.com/heroku/buildpacks-go/compare/v0.1.5...v0.1.6
 [0.1.5]: https://github.com/heroku/buildpacks-go/compare/v0.1.4...v0.1.5
 [0.1.4]: https://github.com/heroku/buildpacks-go/compare/v0.1.3...v0.1.4
 [0.1.3]: https://github.com/heroku/buildpacks-go/compare/v0.1.2...v0.1.3
 [0.1.2]: https://github.com/heroku/buildpacks-go/compare/v0.1.1...v0.1.2
 [0.1.1]: https://github.com/heroku/buildpacks-go/compare/v0.1.0...v0.1.1
-[0.1.0]: https://github.com/heroku/buildpacks-go/releases/tag/v0.1.0
+[0.1.0]: https://github.com/heroku/buildpacks-go/releases/tag/v0.1.0

buildpack.toml

@@ -2,7 +2,7 @@ api = "0.9"
 
 [buildpack]
 id = "heroku/go"
-version = "0.1.7"
+version = "0.1.8"
 name = "Heroku Go"
 homepage = "https://github.com/heroku/buildpacks-go"
 keywords = ["go", "golang", "heroku"]