Add improved docs

Author: wooorm

readme.md

@@ -8,22 +8,68 @@
 [![Backers][backers-badge]][collective]
 [![Chat][chat-badge]][chat]
 
-Parse the YAML front matter in a [`vfile`][vfile].
+[vfile][] utility parse YAML front matter.
 
-## Install
+## Contents
+
+*   [What is this?](#what-is-this)
+*   [When should I use this?](#when-should-i-use-this)
+*   [Install](#install)
+*   [Use](#use)
+*   [API](#api)
+    *   [`matter(file[, options])`](#matterfile-options)
+*   [Types](#types)
+*   [Compatibility](#compatibility)
+*   [Contribute](#contribute)
+*   [License](#license)
+
+## What is this?
+
+This package parses YAML frontmatter, when found in a file, and exposes it as
+`file.data.matter`.
+It can optionally strip the frontmatter, which is useful for languages that do
+not understand frontmatter, but stripping can make it harder to deal with
+languages that *do* understand it, such as markdown, because it messes up
+positional info of warnings and errors.
 
-This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
-Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+## When should I use this?
+
+Frontmatter is a metadata format in front of content.
+It’s typically written in YAML and is often used with markdown.
+This mechanism works well when you want authors, that have some markup
+experience, to configure where or how the content is displayed or supply
+metadata about content.
+
+When using vfiles with markdown, you are likely also using [remark][], in which
+case you should use [`remark-frontmatter`][remark-frontmatter], instead of
+stripping frontmatter.
+
+## Install
 
-[npm][]:
+This package is [ESM only][esm].
+In Node.js (version 12.20+, 14.14+, or 16.0+), install with [npm][]:
 
 ```sh
 npm install vfile-matter
 ```
 
+In Deno with [`esm.sh`][esmsh]:
+
+```js
+import {matter} from 'https://esm.sh/vfile-matter@3'
+```
+
+In browsers with [`esm.sh`][esmsh]:
+
+```html
+<script type="module">
+  import {matter} from 'https://esm.sh/vfile-matter@3?bundle'
+</script>
+```
+
 ## Use
 
-Say we have a file, `example.html`:
+Say our document `example.html` contains:
 
 ```html
 ---
@@ -32,21 +78,21 @@ title: Hello, world!
 <p>Some more text</p>
 ```
 
-And our script, `example.js`, looks like so:
+…and our module `example.js` looks as follows:
 
 ```js
-import {toVFile as vfile} from 'to-vfile'
+import {read} from 'to-vfile'
 import {matter} from 'vfile-matter'
 
-var file = vfile.readSync('example.html')
+const file = await read('example.html')
 
 matter(file, {strip: true})
 
 console.log(file.data)
 console.log(String(file))
 ```
 
-Now, running our script (`node example`) yields:
+…now running `node example.js` yields:
 
 ```js
 {matter: {title: 'Hello, world!'}}
@@ -58,7 +104,7 @@ Now, running our script (`node example`) yields:
 
 ## API
 
-This package exports the following identifiers: `matter`.
+This package exports the identifier `matter`.
 There is no default export.
 
 ### `matter(file[, options])`
@@ -69,18 +115,52 @@ Parse the YAML front matter in a [`vfile`][vfile], and add it as
 If no matter is found in the file, nothing happens, except that
 `file.data.matter` is set to an empty object (`{}`).
 
-###### Parameters
+##### `options`
 
-*   `file` ([`VFile`][vfile])
-    — Virtual file
-*   `options.strip` (`boolean`, default: `false`)
-    — Remove the YAML front matter from the file
-*   `options.yaml` (`Object`, default: `{}`)
-    — Options passed to `jsYaml.load()`
+Configuration (optional).
+
+###### `options.strip`
+
+Remove the YAML front matter from the file (`boolean`, default: `false`).
+
+###### `options.yaml`
+
+Options for the YAML parser (default: `{}`).
+These are passed to [`yaml`][yaml] as `x` in `yaml.parse('', x)`, which is
+equivalent to the combination of
+[`ParseOptions`](https://eemeli.org/yaml/#parse-options),
+[`DocumentOptions`](https://eemeli.org/yaml/#document-options),
+[`SchemaOptions`](https://eemeli.org/yaml/#schema-options), and
+[`ToJsOptions`](https://eemeli.org/yaml/#tojs-options).
 
 ###### Returns
 
-The given `file`.
+The given `file` ([`VFile`][vfile]).
+
+## Types
+
+This package is fully typed with [TypeScript][].
+It exports the additional types `YamlOptions` and `Options`.
+
+To type `file.data.matter`, you can augment `DataMap` from `vfile` as follows:
+
+```ts
+declare module 'vfile' {
+  interface DataMap {
+    matter: {
+      // `file.data.matter.string` is typed as `string?`.
+      title?: string
+    }
+  }
+}
+```
+
+## Compatibility
+
+Projects maintained by the unified collective are compatible with all maintained
+versions of Node.js.
+As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+.
+Our projects sometimes work with older versions, but this is not guaranteed.
 
 ## Contribute
 
@@ -126,16 +206,28 @@ abide by its terms.
 
 [npm]: https://docs.npmjs.com/cli/install
 
-[contributing]: https://github.com/vfile/.github/blob/HEAD/contributing.md
+[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
+
+[esmsh]: https://esm.sh
+
+[typescript]: https://www.typescriptlang.org
 
-[support]: https://github.com/vfile/.github/blob/HEAD/support.md
+[contributing]: https://github.com/vfile/.github/blob/main/contributing.md
+
+[support]: https://github.com/vfile/.github/blob/main/support.md
 
 [health]: https://github.com/vfile/.github
 
-[coc]: https://github.com/vfile/.github/blob/HEAD/code-of-conduct.md
+[coc]: https://github.com/vfile/.github/blob/main/code-of-conduct.md
 
 [license]: license
 
 [author]: https://wooorm.com
 
 [vfile]: https://github.com/vfile/vfile
+
+[remark]: https://github.com/remarkjs/remark
+
+[remark-frontmatter]: https://github.com/remarkjs/remark-frontmatter
+
+[yaml]: https://github.com/eemeli/yaml