add erusev/parsedown

clients/php/composer.json

@@ -1,7 +1,8 @@
 {
   "require": {
     "grpc/grpc": "v1.57.0",
-    "google/protobuf": "v3.23.2"
+    "google/protobuf": "v3.23.2",
+    "erusev/parsedown": "^1.7"
   },
   "autoload": {
     "psr-4": {