docs: Mention installing from MELPA.

Author: szermatt

README.md

@@ -53,6 +53,11 @@ Install Turtles:
     (eldev-use-vc-repository 'turtles :github "szermatt/turtles" :commit "1.0.0")
   ```
 
+- from [MELPA](https://melpa.org/#/getting-started), by typing `M-x
+  package-install turtles`. Note that there's no practical difference
+  between the stable and unstable melpa package, as development
+  happens on a branch. You'll always get the latest release.
+
 Turtles requires Emacs 26.1 or later. Emacs 29.1 or later is recommended.
 
 ## How it works

docs/source/install.rst

@@ -17,6 +17,14 @@ Install Turtles:
     (use-package turtles
       :straight (:type git :repo "https://github.com/szermatt/turtles.git"))
 
+- from `MELPA <https://melpa.org/#/getting-started>`_, by typing `M-x
+  package-install turtles`.
+
+  Note that there's no practical difference between the stable and
+  unstable MELPA package, as development happens on a branch. Both
+  stable and unstable include the latest release of the code, unstable
+  may contain a more recent version of the .info doc.
+
 - the old-fashioned way, copying the .el files from into your
   :file:`.emacs.d` directory.
 

turtles.texi

@@ -164,6 +164,14 @@ from source, using an alternative package managers, such as straight@footnote{ht
   :straight (:type git :repo "https://github.com/szermatt/turtles.git"))
 @end example
 
+@item 
+from MELPA@footnote{https://melpa.org/#/getting-started}, by typing @cite{M-x package-install turtles}.
+
+Note that there’s no practical difference between the stable and
+unstable MELPA package, as development happens on a branch. Both
+stable and unstable include the latest release of the code, unstable
+may contain a more recent version of the .info doc.
+
 @item 
 the old-fashioned way, copying the .el files from into your
 @code{.emacs.d} directory.