docs: add stub stdlib/memory, mark guide as done.

docs/guide.rst

@@ -8,10 +8,6 @@ Language guide
 
 .. py:currentmodule:: amaranth.hdl
 
-.. warning::
-
-   This guide is a work in progress and is seriously incomplete!
-
 This guide introduces the Amaranth language in depth. It assumes familiarity with synchronous digital logic and the Python programming language, but does not require prior experience with any hardware description language. See the :doc:`tutorial <tutorial>` for a step-by-step introduction to the language, and the :doc:`reference <reference>` for a detailed description of the Python classes that underlie the language's syntax.
 
 .. TODO: link to a good synchronous logic tutorial and a Python tutorial?
@@ -1606,7 +1602,7 @@ The renaming of the ``sync`` clock domain in it causes the behavior of the final
 Memories
 ========
 
-.. todo:: Write this section.
+Amaranth provides support for memories in the standard library module :mod:`amaranth.lib.memory`.
 
 
 .. _lang-instance:

docs/stdlib.rst

@@ -17,6 +17,7 @@ The Amaranth standard library is separate from the Amaranth language: everything
    stdlib/enum
    stdlib/data
    stdlib/wiring
+   stdlib/memory
    stdlib/cdc
    stdlib/coding
    stdlib/fifo

docs/stdlib/memory.rst

@@ -0,0 +1,10 @@
+Memories
+--------
+
+.. py:module:: amaranth.lib.memory
+
+The :mod:`amaranth.lib.memory` module provides a way to efficiently store data organized as an array of identically shaped rows, which may be addressed (read and/or written) one at a time.
+
+.. todo::
+
+    Write the rest of this document.