feat: setup Yarn workspaces

Author: Kocal

.gitignore

@@ -1 +1,4 @@
 .php_cs.cache
+node_modules
+yarn.lock
+yarn-error.log

package.json

@@ -0,0 +1,4 @@
+{
+  "private": true,
+  "workspaces": ["src/*/Resources/assets"]
+}