docs(proxy-state-tree): update docs

Author: christianalfoni

packages/node_modules/proxy-state-tree/README.md

@@ -49,7 +49,7 @@ const paths = tree.clearPathsTracking(trackId)
 console.log(paths) // Set { 'foo', 'bar' }
 ```
 
-You would typically use this mechanism to track usage of state. For example rendering a component, calculating a a computed value etc. The returned paths array is stored for later usage. The paths structure is used internally by proxy-state-tree, but you can also consume it as a library author to for example showing components and what paths they depend on in a devtool. Nested paths uses dot notation, for example `['foo.bar']`. Path tracking can be nested, but they can not run at the same time. Meaning the nested tracking must finish before the outer tracker.
+You would typically use this mechanism to track usage of state. For example rendering a component, calculating a a computed value etc. The returned paths set is stored for later usage. The paths structure is used internally by proxy-state-tree, but you can also consume it as a library author to for example showing components and what paths they depend on in a devtool. Nested paths uses dot notation, for example `['foo.bar']`. Path tracking needs to be synchronous from the beginning of the tracking, but the clearing of tracking can be asynchronous.
 
 ## Track mutations
 
@@ -102,7 +102,7 @@ function render () {
   return tree.clearPathsTracking(trackId)
 }
 
-const listener = tree.addMutationListener(render(), () => {
+const listener = tree.addMutationListener(render(), (flushId) => {
   // Runs when mutations matches paths passed in
 
   // Whenever mutations affecting these paths occurs
@@ -137,7 +137,7 @@ const tree = new ProxyStateTree({
 })
 const state = tree.get()
 
-const listener = tree.addMutationListener((mutations) => {
+const listener = tree.addMutationListener((mutations, flushId) => {
   /*
     [{
       method: "set",