Trivial fix typo (#2590)

Although it is spelling mistakes, it might make an affects
while reading.
Signed-off-by: Nguyen Hai Truong <truongnh@vn.fujitsu.com>

plugin/import/README.md

@@ -6,7 +6,7 @@
 
 ## Description
 
-The *import* plugin can be used to incude files into the main configuration. Another use it to
+The *import* plugin can be used to include files into the main configuration. Another use it to
 reference predefined snippets. Both can help to avoid some duplication.
 
 This is a unique directive in that *import* can appear outside of a server block. In other words, it