CH05::Tech details: new section name & intro

Previously this section described all the "best practices" technologies
in detail.  We dropped the best practices section, since there are
multiple valid alternatives, so we need to describe now why we're only
focusing on a subset of the available technologies.

ch05.asciidoc

@@ -581,10 +581,23 @@ increasingly adopting support for explicit paths using descriptors.
 Applications which do both will usually conform to the standards for
 implicit paths and also provide descriptors.
 
-=== Wallet Technology Details
-
-Let's now examine each of the important industry standards that are used
-by many bitcoin wallets in detail.
+=== A Wallet Technology Stack In Detail
+
+Developers of modern wallets can choose from a variety of different
+technologies to help users create and use backups--and new solutions
+appear every year.  Instead of going into detail about each of the
+options we described earlier in this chapter, we'll focus the rest of
+this chapter on the stack of technologies that we think is most widely
+used in wallets as of early 2023:
+
+- BIP39 recovery codes
+- BIP32 Hierarchical Deterministic (HD) key derivation
+- BIP44-style implicit paths
+
+All of these standards have been around since 2014 or earlier and
+you'll have no problem finding additional resources for using them.
+However, if you're feeling bold, we do encourage you to investigate more
+modern standards that may provide additional features or safety.
 
 [[mnemonic_code_words]]
 ==== Mnemonic Code Words (BIP39)