Add forgotten backtick

`truncate_to_first_and_last` is not properly displayed because the ending backtick is not there.

README.md

@@ -413,7 +413,7 @@ Customizations available are:
 |`truncate_from_right`|Just leaves the beginning of a folder name untouched. E.g. your folders will be truncated like so: "/ro../Pr../office". How many characters will be untouched is controlled by `POWERLEVEL9K_SHORTEN_DIR_LENGTH`.|
 |`truncate_absolute`|Truncates everything exept the last few characters in the path. E.g. if you are in a folder named "~/Projects/powerlevel9k" and you have set `POWERLEVEL9K_SHORTEN_DIR_LENGTH=3`, you will get "..l9k".|
 |`truncate_to_last`|Truncates everything before the last folder in the path.|
-|`truncate_to_first_and_last|Truncate middle directories from the path. How many directories will be untouched is controlled by POWERLEVEL9K_SHORTER_DIR_LENGTH. E.g. if you are in a folder named "~/Projects/powerlevel9k" and you have set `POWERLEVEL9K_SHORTEN_DIR_LENGTH=1`, you will get "~/../powerlevel9k".||
+|`truncate_to_first_and_last`|Truncate middle directories from the path. How many directories will be untouched is controlled by POWERLEVEL9K_SHORTER_DIR_LENGTH. E.g. if you are in a folder named "~/Projects/powerlevel9k" and you have set `POWERLEVEL9K_SHORTEN_DIR_LENGTH=1`, you will get "~/../powerlevel9k".||
 |`truncate_to_unique`|Parse all parent path components and truncate them to the shortest unique length. If you copy & paste the result to a shell, after hitting `TAB` it should expand to the original path unambiguously.|
 |`truncate_with_package_name`|Search for a `package.json` or `composer.json` and prints the `name` field to abbreviate the directory path. The precedence and/or files could be set by `POWERLEVEL9K_DIR_PACKAGE_FILES=(package.json composer.json)`. If you have [jq](https://stedolan.github.io/jq/) installed, it will dramatically improve the speed of this strategy.|
 |`truncate_with_folder_marker`|Search for a file that is specified by `POWERLEVEL9K_SHORTEN_FOLDER_MARKER` and truncate everything before that (if found, otherwise stop on $HOME and ROOT).|