chore(): Reorganize modules (#7210)

**What**
Move all modules to the modules directory

packages/modules/cache-inmemory/README.md

@@ -0,0 +1,23 @@
+# Medusa Cache In-memory
+
+Medusa in-memory cache module. Use plain JS Map as a cache store.
+
+## Installation
+
+```
+yarn add @medusajs/cache-inmemory
+```
+
+## Options
+
+```
+{
+  ttl?: number // Time to keep data in cache (in seconds)
+}
+```
+
+### Note
+Recommended for testing and development. For production, use Redis cache module. 
+
+### Other caching modules
+- [Medusa Cache Redis](../cache-redis/README.md)