docs: add docs for editorconfig to configuration and options (#11883)

docs/configuration.md

@@ -173,3 +173,12 @@ You can also switch to the `flow` parser instead of the default `babel` for .js
 ## Configuration Schema
 
 If you’d like a JSON schema to validate your configuration, one is available here: http://json.schemastore.org/prettierrc.
+
+## EditorConfig
+
+If `options.editorconfig` is `true` and an [`.editorconfig` file](https://editorconfig.org/) is in your project, Prettier will parse it and convert its properties to the corresponding Prettier configuration. This configuration will be overridden by `.prettierrc`, etc. Currently, the following EditorConfig properties are supported:
+
+- `end_of_line`
+- `indent_style`
+- `indent_size`/`tab_width`
+- `max_line_length`

docs/options.md

@@ -27,6 +27,8 @@ Specify the line length that the printer will wrap on.
 | ------- | --------------------- | ------------------- |
 | `80`    | `--print-width <int>` | `printWidth: <int>` |
 
+Setting `max_line_length` in an [`.editorconfig` file](https://editorconfig.org/) will configure Prettier’s print width, unless overridden.
+
 (If you don’t want line wrapping when formatting Markdown, you can set the [Prose Wrap](#prose-wrap) option to disable it.)
 
 ## Tab Width
@@ -37,6 +39,8 @@ Specify the number of spaces per indentation-level.
 | ------- | ------------------- | ----------------- |
 | `2`     | `--tab-width <int>` | `tabWidth: <int>` |
 
+Setting `indent_size` or `tab_width` in an [`.editorconfig` file](https://editorconfig.org/) will configure Prettier’s tab width, unless overridden.
+
 ## Tabs
 
 Indent lines with tabs instead of spaces.
@@ -45,6 +49,8 @@ Indent lines with tabs instead of spaces.
 | ------- | ------------ | ----------------- |
 | `false` | `--use-tabs` | `useTabs: <bool>` |
 
+Setting `indent_style` in an [`.editorconfig` file](https://editorconfig.org/) will configure Prettier’s tab usage, unless overridden.
+
 (Tabs will be used for _indentation_ but Prettier uses spaces to _align_ things, such as in ternaries.)
 
 ## Semicolons
@@ -425,6 +431,8 @@ Valid options:
 | ------- | ----------------------------------------------------------- | ---------------------------------------------------------- |
 | `"lf"`  | <code>--end-of-line <lf&#124;crlf&#124;cr&#124;auto></code> | <code>endOfLine: "<lf&#124;crlf&#124;cr&#124;auto>"</code> |
 
+Setting `end_of_line` in an [`.editorconfig` file](https://editorconfig.org/) will configure Prettier’s end of line usage, unless overridden.
+
 ## Embedded Language Formatting
 
 _First available in v2.1.0_