Add 'Known Issues' section to README.md (#91)

Author: ManlyMarco

README.md

@@ -15,6 +15,9 @@ There are two versions of this plugin, for BepInEx 5 (version 5.4.20 or newer, m
 
 Note: The .xml file include in the release zip is useful for plugin developers when referencing ConfigurationManager.dll in your plugin, it will provide descriptions for types and methods to your IDE. Users can ignore it.
 
+### Known issues
+- If no text is visible anywhere in RUE windows, most likely the `Arial.ttf` font is missing from the system (Unity UI default font, may be different in some games). This can happen when running a game on Linux with [misconfigured wine](https://github.com/ManlyMarco/RuntimeUnityEditor/issues/55).
+
 ## How to make my mod compatible?
 ConfigurationManager will automatically display all settings from your plugin's `Config`. All metadata (e.g. description, value range) will be used by ConfigurationManager to display the settings to the user.