doc: fix extname with the correct description

PR-URL: #27303
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>

doc/api/path.md

@@ -157,9 +157,9 @@ changes:
 
 The `path.extname()` method returns the extension of the `path`, from the last
 occurrence of the `.` (period) character to end of string in the last portion of
-the `path`. If there is no `.` in the last portion of the `path`, or if the
-first character of the basename of `path` (see `path.basename()`) is `.`, then
-an empty string is returned.
+the `path`. If there is no `.` in the last portion of the `path`, or if
+there are no `.` characters other than the first character of
+the basename of `path` (see `path.basename()`) , an empty string is returned.
 
 ```js
 path.extname('index.html');
@@ -176,6 +176,9 @@ path.extname('index');
 
 path.extname('.index');
 // Returns: ''
+
+path.extname('.index.md');
+// Returns: '.md'
 ```
 
 A [`TypeError`][] is thrown if `path` is not a string.