doc: clarify the position argument for fs.read

doc: clarify the position argument for fs.read · nodejs/node@5a7a49f

Original file line number	Diff line number	Diff line change
@@ -1309,7 +1309,9 @@ Read data from the file specified by `fd`.
`1309`	`1309`	`length` is an integer specifying the number of bytes to read.
`1310`	`1310`
`1311`	`1311`	`position` is an integer specifying where to begin reading from in the file.
`1312`		-If `position` is `null`, data will be read from the current file position.
	`1312`	+If `position` is `null`, data will be read from the current file position,
	`1313`	`+and the file position will be updated for subsequent reads.`
	`1314`	+If `position` is an integer, the file position will remain unchanged.
`1313`	`1315`
`1314`	`1316`	The callback is given the three arguments, `(err, bytesRead, buffer)`.
`1315`	`1317`