config.txt: add missing period

Signed-off-by: Kyle Meyer <kyle@kyleam.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -46,7 +46,7 @@ Subsection names are case sensitive and can contain any characters except
 newline and the null byte. Doublequote `"` and backslash can be included
 by escaping them as `\"` and `\\`, respectively. Backslashes preceding
 other characters are dropped when reading; for example, `\t` is read as
-`t` and `\0` is read as `0` Section headers cannot span multiple lines.
+`t` and `\0` is read as `0`. Section headers cannot span multiple lines.
 Variables may belong directly to a section or to a given subsection. You
 can have `[section]` if you have `[section "subsection"]`, but you don't
 need to.