add cookbook about Emacs integration (#2506)

* add cookbook about Emacs integration

This documents how to simplify usage of Scala CLI repl from within
Emacs.

(This is a followup on this discussion #2501)

* Update sidebar position for the Emacs cookbook

---------

Co-authored-by: Piotr Chabelski <ged.subfan@gmail.com>

website/docs/cookbooks/emacs.md

@@ -0,0 +1,30 @@
+---
+title: Scala CLI within Emacs
+sidebar_position: 14
+---
+
+Emacs users can make it easier to use Scala CLI from within their editor by
+loading an extension: <https://github.com/ag91/scala-cli-repl>.
+
+That lets you send Scala code directly from your buffer to the Scala REPL.
+
+![scala-cli-repl-demo](/img/scala-cli-repl.jpg)
+
+The extension also facilitates [literate
+programming](https://en.wikipedia.org/wiki/Literate_programming) using
+[Org Mode](https://orgmode.org/), by letting the user experiment with
+source blocks looking like the following.
+
+``` org
+#+begin_src scala :scala-version 3.0.0 :dep '("com.lihaoyi::os-lib:0.9.0")
+println("This is:" + os.pwd)
+#+end_src
+#+end_src
+```
+
+In the above you can see that you can select the Scala version and
+dependencies you need for your code.
+
+The users who use [lsp-metals](https://github.com/emacs-lsp/lsp-metals)
+can also enable lsp support within a source block to access utilities as
+completion and navigation from within the Org Mode file.

website/docs/cookbooks/intro.md

@@ -29,6 +29,7 @@ To get started, try one of the cookbooks below:
 - [IDEA IntelliJ](./intellij.md)
 - [Scala CLI alongside SBT in IDEA IntelliJ](./intellij-sbt-with-bsp.md)
 - [Multiple Scala CLI projects as separate modules in IDEA IntelliJ](./intellij-multi-bsp.md)
+- [Scala CLI within Emacs](./emacs.md)
 
 ## Packaging ⚡️