docs: Add note about open/closing surrounds to README.

Resolves #410

Author: kylechui

README.md

@@ -73,6 +73,7 @@ respectively. For the following examples, `*` will denote the cursor position:
     Old text                    Command         New text
 --------------------------------------------------------------------------------
     surr*ound_words             ysiw)           (surround_words)
+    surr*ound_words             ysiw(           ( surround_words )
     *make strings               ys$"            "make strings"
     [delete ar*ound me!]        ds]             delete around me!
     remove <b>HTML t*ags</b>    dst             remove HTML tags
@@ -81,7 +82,9 @@ respectively. For the following examples, `*` will denote the cursor position:
     delete(functi*on calls)     dsf             function calls
 ```
 
-Detailed information on how to use this plugin can be found in
+Note that surrounding with an opening delimiter (e.g. `(`) will add a space before/after
+the selection, while surrounding with the closing delimiter (e.g. `)`) will not include
+the spaces. Detailed information on how to use this plugin can be found in
 [`:h nvim-surround.usage`](https://github.com/kylechui/nvim-surround/blob/main/doc/nvim-surround.txt).
 
 ## :gear: Configuration