Add --enable-redis-zstd to install docs

Author: fitztrev

Changelog.md

@@ -13,7 +13,7 @@ and PhpRedis adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Added
 
-- Add optional support for Zstd compression, using `--enable-redis-ztsd`.
+- Add optional support for Zstd compression, using `--enable-redis-zstd`.
   This requires libzstd version >= 1.3.0
   [2abc61da](https://github.com/phpredis/phpredis/commit/2abc61da)
   ([Remi Collet](https://github.com/remicollet))

INSTALL.markdown

@@ -12,7 +12,7 @@ To build this extension for the sources tree:
 
 ~~~
 phpize
-./configure [--enable-redis-igbinary] [--enable-redis-msgpack] [--enable-redis-lzf [--with-liblzf[=DIR]]]
+./configure [--enable-redis-igbinary] [--enable-redis-msgpack] [--enable-redis-lzf [--with-liblzf[=DIR]]] [--enable-redis-zstd]
 make && make install
 ~~~