Add What can't be fixed and info about player heads (#1680)

* Add What can't be fixed and info about player heads

* Update README.md

README.md

@@ -48,6 +48,11 @@ Take a look [here](https://github.com/GeyserMC/Geyser/wiki#Setup) for how to set
   - Loom
   - Smithing Table
 
+## What can't be fixed
+The following things can't be fixed because of Bedrock limitations. They might be fixable in the future, but not as of now.
+
+- Custom heads in inventories
+
 ## Compiling
 1. Clone the repo to your computer
 2. [Install Maven](https://maven.apache.org/install.html)