chore: specify versions for FE tools, fix doc links (#2464)

Author: darrenjaneczek

README.md

@@ -144,7 +144,7 @@ Pyroscope is possible thanks to the excellent work of many people, including but
 
 ## Contributing
 
-To start contributing, check out our [Contributing Guide](CONTRIBUTING.md)
+To start contributing, check out our [Contributing Guide](docs/internal/contributing/README.md)
 
 
 ### Thanks to the contributors of Pyroscope!

docs/internal/contributing/README.md

@@ -78,6 +78,10 @@ replace `image: grafana/pyroscope` with the local tag name you got from docker-i
 
 #### Front end development
 
+**Versions for development tools**:
+- Node v18
+- Yarn v1.22
+
 The front end code is all located in the `public/app` directory, although its `plugin.json`
 file exists at the repository root.