update docs

Author: mxjp

docs/installation.md

@@ -1,11 +1,19 @@
 # Installation
 
-## Npm Package
+## Npm
 Rvx is available as an [npm package](https://www.npmjs.com/package/rvx).
 ```bash
 npm i rvx
 ```
 
+### Conflicting Dependencies
+Using multiple rvx instances at the same time will result in undefined behavior.
+
+You can check with `npm ls` that only one instance is installed:
+```bash
+npm ls rvx
+```
+
 ## Buildless Options
 Rvx can be used without any build system by directly using one of the es module bundles listed below. Note, that these bundles don't include any JSX related code.