Add version detection chapter to README

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nenv"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2021"
 
 

README.md

@@ -6,7 +6,7 @@ Node environment manager written in rust.
 
 - Written in fast and safe rust
 - Multiple active nodejs versions at the same time
-- Configuration for project specific versions with the `engines.node` field in the package.json
+- Configuration for project specific versions
 - Version matching with semver expressions
 
 ## Installation
@@ -55,6 +55,28 @@ nenv list-versions
 ```
 
 
+## Version detection
+
+The node version nenv uses is controlled by
+
+1. The `engines.node` config field in the `package.json` which is parsed as a semver requirement.
+```json
+{
+  "name": "my project",
+  "engines": {
+    "node": "18"
+  }
+}
+```
+
+2. The `.node-version` file in the current or parent directories which contains the version string.
+```
+19.4.0  
+```
+
+3. The `NODE_VERSION` environment variable.
+4. The default version set with `nenv default`.
+
 ## License
 
 GPL-3.0