Document flexmark formatter

Author: korthout

README.md

@@ -64,6 +64,7 @@ lib('kotlin.KtLintStep')                         +'{{yes}}       | {{yes}}
 lib('kotlin.KtfmtStep')                          +'{{yes}}       | {{yes}}      | {{no}}       | {{no}}  |',
 lib('kotlin.DiktatStep')                         +'{{yes}}       | {{yes}}      | {{no}}       | {{no}}  |',
 lib('markdown.FreshMarkStep')                    +'{{yes}}       | {{no}}       | {{no}}       | {{no}}  |',
+lib('markdown.FlexmarkStep')                     +'{{no}}        | {{yes}}      | {{no}}       | {{no}}  |',
 lib('npm.PrettierFormatterStep')                 +'{{yes}}       | {{yes}}      | {{no}}       | {{no}}  |',
 lib('npm.TsFmtFormatterStep')                    +'{{yes}}       | {{yes}}      | {{no}}       | {{no}}  |',
 lib('pom.SortPomStepStep')                       +'{{no}}        | {{yes}}      | {{no}}       | {{no}}  |',
@@ -103,6 +104,7 @@ extra('wtp.EclipseWtpFormatterStep')             +'{{yes}}       | {{yes}}
 | [`kotlin.KtfmtStep`](lib/src/main/java/com/diffplug/spotless/kotlin/KtfmtStep.java) | :+1:       | :+1:      | :white_large_square:       | :white_large_square:  |
 | [`kotlin.DiktatStep`](lib/src/main/java/com/diffplug/spotless/kotlin/DiktatStep.java) | :+1:       | :+1:      | :white_large_square:       | :white_large_square:  |
 | [`markdown.FreshMarkStep`](lib/src/main/java/com/diffplug/spotless/markdown/FreshMarkStep.java) | :+1:       | :white_large_square:       | :white_large_square:       | :white_large_square:  |
+| [`markdown.FlexmarkStep`](lib/src/main/java/com/diffplug/spotless/markdown/FlexmarkStep.java) | :white_large_square:       | :+1:       | :white_large_square:       | :white_large_square:  |
 | [`npm.PrettierFormatterStep`](lib/src/main/java/com/diffplug/spotless/npm/PrettierFormatterStep.java) | :+1:       | :+1:      | :white_large_square:       | :white_large_square:  |
 | [`npm.TsFmtFormatterStep`](lib/src/main/java/com/diffplug/spotless/npm/TsFmtFormatterStep.java) | :+1:       | :+1:      | :white_large_square:       | :white_large_square:  |
 | [`pom.SortPomStepStep`](lib/src/main/java/com/diffplug/spotless/pom/SortPomStepStep.java) | :white_large_square:        | :+1:      | :white_large_square:       | :white_large_square:  |

plugin-maven/README.md

@@ -56,6 +56,7 @@ user@machine repo % mvn spotless:check
   - [Antlr4](#antlr4) ([antlr4formatter](#antlr4formatter))
   - [Sql](#sql) ([dbeaver](#dbeaver))
   - [Maven Pom](#maven-pom) ([sortPom](#sortpom))
+  - [Markdown](#markdown) ([flexmark](#flexmark))
   - [Typescript](#typescript) ([tsfmt](#tsfmt), [prettier](#prettier))
   - Multiple languages
     - [Prettier](#prettier) ([plugins](#prettier-plugins), [npm detection](#npm-detection), [`.npmrc` detection](#npmrc-detection))
@@ -585,6 +586,30 @@ All configuration settings are optional, they are described in detail [here](htt
 </sortPom>
 ```
 
+## Markdown
+
+[code](https://github.com/diffplug/spotless/blob/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/markdown/Markdown.java). [available steps](https://github.com/diffplug/spotless/tree/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/markdown).
+
+```xml
+<configuration>
+  <markdown>
+    <!-- These are the defaults, you can override if you want -->
+    <includes>
+      <include>*.md</include>
+      <include>**/*.md</include>
+    </includes>
+
+    <flexmark/> <!-- has its own section below -->
+  </markdown>
+</configuration>
+```
+
+### Flexmark
+
+[homepage](https://github.com/vsch/flexmark-java). [code](https://github.com/diffplug/spotless/blob/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/markdown/Flexmark.java).
+
+None of the available options can be configured yet. Currently it uses only the default options together with `COMMONMARK` as `FORMATTER_EMULATION_PROFILE`. All options are described in detail [here](https://github.com/vsch/flexmark-java/wiki/Markdown-Formatter#options).
+
 <a name="applying-to-typescript-source"></a>
 
 ## Typescript