chore: switch to Yarn

extensions/markdown/.gitignore

@@ -3,4 +3,13 @@ composer.phar
 .DS_Store
 Thumbs.db
 bower_components
-node_modules
+node_modules
+
+# Yarn 2+
+js/.pnp.*
+js/.yarn/*
+!js/.yarn/patches
+!js/.yarn/plugins
+!js/.yarn/releases
+!js/.yarn/sdks
+!js/.yarn/versions

extensions/markdown/js/.yarnrc.yml

@@ -0,0 +1,3 @@
+nodeLinker: node-modules
+
+yarnPath: .yarn/releases/yarn-3.1.1.cjs

extensions/markdown/js/package.json

@@ -2,12 +2,13 @@
   "private": true,
   "name": "@flarum/markdown",
   "dependencies": {
-    "flarum-webpack-config": "^1.0",
+    "flarum-webpack-config": "^1.0.0",
     "webpack": "^4.46.0",
     "webpack-cli": "^4.9.1"
   },
   "scripts": {
     "dev": "webpack --mode development --watch",
     "build": "webpack --mode production"
-  }
+  },
+  "packageManager": "yarn@3.1.1"
 }