Move puffin changelog and release.toml to puffin/ (#196)

Also add a section to the README about releasing.

README.md

@@ -75,6 +75,13 @@ We welcome community contributions to this project.
 
 Please read our [Contributor Guide](CONTRIBUTING.md) for more information on how to get started.
 
+## Releasing
+
+We use the [cargo release](https://github.com/crate-ci/cargo-release) tool to manage changelogs, git tags and publishing crates.
+
+Each substantial pull request should add a changelog entry under the `[Unreleased]` section (see [keep a changelog](https://keepachangelog.com)
+and previous changelog entries). The crate version in `Cargo.toml` is never updated manually in a PR as it's handled by `cargo release`.
+
 ## License
 
 Licensed under either of

puffin/release.toml

@@ -0,0 +1,10 @@
+pre-release-commit-message = "Release puffin-{{version}}"
+tag-message = "Release puffin-{{version}}"
+tag-name = "puffin-{{version}}"
+pre-release-replacements = [
+    { file = "CHANGELOG.md", search = "Unreleased", replace = "{{version}}" },
+    { file = "CHANGELOG.md", search = "\\.\\.\\.HEAD", replace = "...{{tag_name}}" },
+    { file = "CHANGELOG.md", search = "ReleaseDate", replace = "{{date}}" },
+    { file = "CHANGELOG.md", search = "<!-- next-header -->", replace = "<!-- next-header -->\n## [Unreleased] - ReleaseDate" },
+    { file = "CHANGELOG.md", search = "<!-- next-url -->", replace = "<!-- next-url -->\n[Unreleased]: https://github.com/EmbarkStudios/puffin/compare/{{tag_name}}...HEAD" },
+]