Update settings and documentation

`remark-language-server` 3 adds a new setting.

Author: remcohaszing

package.json

@@ -102,6 +102,16 @@
     }
   },
   "contributes": {
+    "configuration": {
+      "title": "remark",
+      "properties": {
+        "remark.requireConfig": {
+          "type": "boolean",
+          "default": false,
+          "markdownDescription": "If true, only perform actions if a [configuration file](https://github.com/remarkjs/remark-language-server#configuration-file) is found."
+        }
+      }
+    },
     "jsonValidation": [
       {
         "fileMatch": [

readme.md

@@ -14,6 +14,8 @@ Visual Studio Code extension to format and lint markdown files with remark.
 * [When should I use this?](#when-should-i-use-this)
 * [Install](#install)
 * [Use](#use)
+* [Configuration file](#configuration-file)
+* [Settings](#settings)
 * [Formatting](#formatting)
 * [Plugins](#plugins)
 * [Compatibility](#compatibility)
@@ -72,6 +74,32 @@ Here’s an example that should produce problems you can use to verify:
 1) Hello, _Jupiter_ and *Neptune*!
 ```
 
+## Configuration file
+
+`remark-language-server` uses the same configuration files as
+[`remark-cli`][remark-cli].
+These files are:
+
+* `.remarkrc`
+* `.remarkrc.cjs`
+* `.remarkrc.js`
+* `.remarkrc.json`
+* `.remarkrc.mjs`
+* `.remarkrc.yaml`
+* `.remarkrc.yml`
+* `package.json`
+
+Language clients should notify the language server if these files change.
+They are looked up starting at the folder where the checked markdown file
+exists.
+
+## Settings
+
+This extension supports the following settings:
+
+* `remark.requireConfig` (`boolean`, default: `false`) — If true, only perform
+  actions if a [configuration file][configuration-file] is found.
+
 ## Formatting
 
 This extension can format markdown files.
@@ -141,6 +169,8 @@ abide by its terms.
 
 [build]: https://github.com/remarkjs/vscode-remark/actions
 
+[configuration-file]: #configuration-file
+
 [downloads-badge]: https://img.shields.io/visual-studio-marketplace/d/unifiedjs.vscode-remark
 
 [chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg