Make root() return destructor automatically

docs/api/reactivity-core.md

@@ -14,18 +14,15 @@ Creates and runs a function in a new stable scope.
 - **Type**
 
     ```lua
-    function root<T...>(fn: (destroy: () -> ()) -> T...): T...
+    function root<T...>(fn: (() -> ()) -> T...): (() -> (), T...)
     ```
 
 - **Details**
 
-    Returns the result of the given function.
+    Returns a function to destroy the root scope. Also passes this function as
+    the first argument into its callback.
 
-    Creates a new stable scope, where creation of effects can be tracked and
-    properly disposed of.
-
-    A function to destroy the root is passed into the callback, which will run
-    any cleanups and allow derived sources created to garbage collect.
+    All values returned by the callback are also returned following the destructor.
 
 ## source()
 

docs/tut/advanced/nested-scoping.md

@@ -81,9 +81,8 @@ mount(function()
 
     effect(function()
         if toggled() then
-            local destroy = root(function(destroy)
+            local destroy = root(function()
                 Counter()
-                return destroy
             end)
             cleanup(destroy)
         end

docs/tut/crash-course/10-cleanup.md

@@ -13,15 +13,13 @@ local effect = vide.effect
 local count = source(0)
 
 
-local destroy = root(function(destroy)
+local destroy = root(function()
     effect(function()
         local x = count()
         cleanup(function() print(x) end)
     end)
 
     cleanup(function() print "root destroyed" end)
-
-    return destroy
 end)
 
 count(1) -- prints "0"

docs/tut/crash-course/6-scope.md

@@ -43,21 +43,20 @@ local count = root(setup) -- ok since effect() was called within a stable scope
 count(1) -- prints "1"
 ```
 
-The scope created by `root()` can be destroyed by calling the function it passes
-into the given function.
+The scope created by `root()` can be destroyed.
 
 ```lua
-local function setup(destroy)
+local function setup()
     local count = source(0)
 
     effect(function()
         print(count())
     end)
 
-    return count, destroy
+    return count
 end
 
-local count, destroy = root(setup)
+local destroy, count = root(setup)
 
 count(1) -- prints "1"