Translation: Update index.md (#1286)

* Translation: Update index.md

simplified the words using "vibrant" instead. used illustrate instead of demonstrate because I'm thinking the image "illustrates" the concept.

* Translation: Update index.md

Changed to what  yuelinxin has suggested. thanks for the suggestion.

en/docs/chapter_tree/index.md

@@ -4,6 +4,6 @@
 
 !!! abstract
 
-    The towering tree, full of vitality with its roots deep and leaves lush, branches spreading wide.
+    The towering tree, vibrant with it's deep roots and lush leaves, branches spreading wide.
     
-    It vividly demonstrates the form of data divide-and-conquer.
+    It vividly illustrates the concept of divide-and-conquer in data.