Add CONTRIBUTING.md and update security policy with breaking change

CONTRIBUTING.md

@@ -0,0 +1,64 @@
+# Contributing
+
+## Setup
+
+```shell
+git clone https://github.com/webdeveric/utils.git
+cd utils
+corepack enable
+pnpm install --frozen-lockfile
+```
+
+### Node.js version
+
+This project uses the Node version in [.node-version](.node-version).
+
+Run `fnm use` or `nvm use` to ensure you're using the correct Node.js version.
+
+## Testing
+
+Run tests in watch mode
+
+```shell
+pnpm test
+```
+
+Run tests and generate a coverage report.
+
+```shell
+pnpm coverage
+```
+
+## Linting, type checking, and spell checking
+
+These all run in CI and must pass before a PR can be merged.
+
+```shell
+pnpm lint
+pnpm typecheck
+pnpm spellcheck
+```
+
+Run `pnpm format` to apply Prettier formatting. A `pre-commit` hook auto-fixes lint/format/spelling issues on staged files, so most of this happens for you on commit.
+
+## Building
+
+```shell
+pnpm build
+```
+
+## Commit messages
+
+Commit messages should follow [conventional commits](https://www.conventionalcommits.org/).
+
+Releases are created automatically and the version bump is determined from the commit messages.
+
+## Pull requests
+
+If you want to add a large feature or breaking change, please open an issue first so it can be discussed.
+
+:warning: Low effort AI generated PRs will be closed without any explanation.
+
+## Security
+
+To report a security vulnerability, see [SECURITY.md](SECURITY.md) instead of opening a public issue.

SECURITY.md

@@ -1,11 +1,14 @@
 # Security Policy
 
-## Supported Versions
+## Supported versions
 
-### `v0.x.x`
+Only the last two major versions are supported.
 
-Until `v1+`, only the latest version is supported.
+| Version | Supported          |
+| ------- | ------------------ |
+| 1.x.x   | :white_check_mark: |
+| 0.x.x   | :x:                |
 
-### `v1.x.x+`
+## Reporting a vulnerability
 
-Only the last two major versions are supported.
+Click the "**Report a vulnerability**" button on [https://github.com/webdeveric/utils/security](https://github.com/webdeveric/utils/security).