Changes: document KCoreAddons dependency

CHANGES

@@ -13,6 +13,11 @@ This release contains contributions from (alphabetically by first name):
   has had a few updates and has now been consistently applied across
   the core codebase (e.g. libcalamares, libcalamaresui, calamares, but
   not the modules).
+- *KCoreAddons* is now a required dependency. This lets us drop a chunk
+  of code that was copied from KCoreAddons years ago, and use the
+  (maintained!) upstream version instead. It also gives us KMacroExpander
+  everywhere, which will simplify code for handling substitutions
+  in configuration files.
 
 ## Modules ##
 

README.md

@@ -21,6 +21,7 @@ Main:
 * Boost.Python >= 1.55.0 (required for some modules)
 * KDE extra-cmake-modules >= 5.18 (recommended; required for some modules;
   required for some tests)
+* KDE Frameworks KCoreAddons (>= 5.58 recommended)
 * PythonQt (optional, deprecated)
 
 Modules: