Add new Markdown option 'breakDefinitions' - Closes prettier#3531

Allows to select if Markdown definitions should be broken when
'proseWrap' is set to 'always'. This enables, for example, single line
reference links, which can prevent potential rendering issues.

src/language-markdown/options.js

@@ -1,9 +1,18 @@
 import commonOptions from "../common/common-options.evaluate.js";
 
+const CATEGORY_MARKDOWN = "Markdown";
+
 // format based on https://github.com/prettier/prettier/blob/main/src/main/core-options.evaluate.js
 const options = {
   proseWrap: commonOptions.proseWrap,
   singleQuote: commonOptions.singleQuote,
+  breakDefinitions: {
+    category: CATEGORY_MARKDOWN,
+    type: "boolean",
+    default: true,
+    description:
+      "Whether or not 'proseWrap' takes effect over Markdown definitions.",
+  }
 };
 
 export default options;

src/language-markdown/printer-markdown.js

@@ -364,7 +364,9 @@ function genericPrint(path, options, print) {
           ];
       }
     case "definition": {
-      const lineOrSpace = options.proseWrap === "always" ? line : " ";
+      const lineOrSpace =
+        options.proseWrap === "always" &&
+        options.breakDefinitions === true ? line : " ";
       return group([
         printLinkReference(node),
         ":",