Update README.md

Author: tokers

README.md

@@ -12,11 +12,11 @@
   - log_by_lua
 
 - api
-  * [ngx.log](chapters/015-ngx_lua_log.md)
-  * ngx.ctx
-  * ngx.sleep
-  * ngx.var.VARIABLES
-  * others
+  - [ngx.log](chapters/015-ngx_lua_log.md)
+  - ngx.ctx
+  - ngx.var.VARIABLES
+  - ngx.sleep
+  - others
 
 - others
   - [ngx_http_lua_cache](chapters/012-ngx_lua_cache.md)