Add Recent Changes section

doc/hash.adoc

@@ -18,6 +18,7 @@ https://www.boost.org/LICENSE_1_0.txt
 :leveloffset: +1
 
 include::hash/intro.adoc[]
+include::hash/recent.adoc[]
 include::hash/tutorial.adoc[]
 include::hash/user.adoc[]
 include::hash/combine.adoc[]

doc/hash/recent.adoc

@@ -0,0 +1,29 @@
+////
+Copyright 2022 Peter Dimov
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
+[#recent]
+= Recent Changes
+:idprefix: recent_
+
+== Boost 1.81.0
+
+Major update.
+
+* The specializations of `boost::hash` have been removed; it now
+  always calls `hash_value`.
+* Support for `BOOST_HASH_NO_EXTENSIONS` has been removed. The
+  extensions are always enabled.
+* All standard containers are now supported. This includes
+  `std::forward_list` and the unordered associative containers.
+* User-defined containers (types that have `begin()` and `end()`
+  member functions that return iterators) are now supported out
+  of the box.
+* `hash_combine` has been improved.
+* The performance (and quality, as a result of the above change)
+  of string hashing has been improved. `boost::hash` for strings
+  now passes SMHasher in 64 bit mode.
+* The documentation has been substantially revised to reflect
+  the changes.