edit Garbage collection

Author: Bunlong

pages/4.2-Garbage-collection.md

@@ -12,7 +12,7 @@ Simply put, “reachable” values are those that are accessible or usable someh
 
 1. There’s a base set of inherently reachable values, that cannot be deleted for obvious reasons.
 
-  For instance:
+   For instance:
 
   * Local variables and parameters of the current function.
 
@@ -22,11 +22,11 @@ Simply put, “reachable” values are those that are accessible or usable someh
 
   * (there are some other, internal ones as well)
 
-  These values are called roots.
+   These values are called roots.
 
 2. Any other value is considered reachable if it’s reachable from a root by a reference or by a chain of references.
 
-  For instance, if there’s an object in a local variable, and that object has a property referencing another object, that object is considered reachable. And those that it references are also reachable. Detailed examples to follow.
+   For instance, if there’s an object in a local variable, and that object has a property referencing another object, that object is considered reachable. And those that it references are also reachable. Detailed examples to follow.
 
 There’s a background process in the JavaScript engine that is called [garbage](https://en.wikipedia.org/wiki/Garbage_collection_(computer_science) "garbage") collector. It monitors all objects and removes those that have become unreachable.