doc: switch the order of Writable and Readable · nodejs/node@e00e5e6

Original file line number	Diff line number	Diff line change
`@@ -37,10 +37,10 @@ the elements of the API that are required to implement new types of streams.`
`37`	`37`
`38`	`38`	`There are four fundamental stream types within Node.js:`
`39`	`39`
`40`		-* [`Readable`][] - streams from which data can be read (for example
`41`		-[`fs.createReadStream()`][]).
`42`	`40`	* [`Writable`][] - streams to which data can be written (for example
`43`	`41`	[`fs.createWriteStream()`][]).
	`42`	+* [`Readable`][] - streams from which data can be read (for example
	`43`	+[`fs.createReadStream()`][]).
`44`	`44`	* [`Duplex`][] - streams that are both `Readable` and `Writable` (for example
`45`	`45`	[`net.Socket`][]).
`46`	`46`	* [`Transform`][] - `Duplex` streams that can modify or transform the data as it