doc: add note regarding special case of 0 stat.size

Refs: #43669

PR-URL: #43690
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Juan José Arboleda <[email protected]>
Reviewed-By: LiviaMedeiros <[email protected]>

Author: dougwilson

doc/api/fs.md

@@ -6639,6 +6639,9 @@ A numeric device identifier if the file represents a device.
 
 The size of the file in bytes.
 
+If the underlying file system does not support getting the size of the file,
+this will be `0`.
+
 #### `stats.blksize`
 
 * {number|bigint}