Update runtime files.

README_VIM9.md

@@ -2,18 +2,17 @@
 
 # What is Vim9?
 
-This is an experimental side of [Vim](https://github.com/vim/vim).
-It explores ways of making Vim script faster and better.
+This is a new syntax for Vim script that was introduced with Vim 9.0.
+It intends making Vim script faster and better.
 
-WARNING: The Vim9 script features are still under development, anything can
-break!
 
 # Why Vim9?
 
 ## 1. FASTER VIM SCRIPT
 
 The third item on the poll results of 2018, after popup windows and text
-properties, is faster Vim script.  So how do we do that?
+properties, both of which have been implemented, is faster Vim script.
+So how do we do that?
 
 I have been throwing some ideas around, and soon came to the conclusion
 that the current way functions are called and executed, with
@@ -53,7 +52,7 @@ we can gain, and also that Vim script can be faster than builtin
 interfaces.
 
 LuaJit is much faster at Lua-only instructions.  In practice the script would
-not do something useless as counting but change the text.  For example,
+not do something useless counting, but change the text.  For example,
 reindent all the lines:
 
 ``` vim