Document what all our patches do

Some of them didn't have documentation, now they all do.

.github/scripts/patches/androiddeployqt_keystore_env.diff

@@ -1,3 +1,6 @@
+Description: Environment variables to control androiddeployqt behavior, see
+comments added in the diff below.
+
 --- a/src/tools/androiddeployqt/main.cpp
 +++ b/src/tools/androiddeployqt/main.cpp
 @@ -405,6 +405,44 @@

.github/scripts/patches/qandroidassetsfileenginehandler_dot_slash.diff

@@ -1,3 +1,8 @@
+Description: Patch Android asset file handler to strip any instance of "./" from
+the paths its given. The icon engine stuffs those in there unconditionally and
+(reasonably) expects that to have no effect, but on Android's weird content URI
+file system, it leads to the paths not resolving anymore.
+
 --- a/src/plugins/platforms/android/qandroidassetsfileenginehandler.cpp	2023-04-26 08:39:21.720887254 +0200
 +++ b/src/plugins/platforms/android/qandroidassetsfileenginehandler.cpp	2023-04-26 08:39:24.477553939 +0200
 @@ -55,6 +55,7 @@

.github/scripts/patches/qmake_android_ltcg.diff

@@ -1,3 +1,5 @@
+Description: Properly pass -ltcg flag through on Android.
+
 --- a/mkspecs/android-clang/qmake.conf    2023-04-02 00:10:00.000000000 -0500
 +++ b/mkspecs/android-clang/qmake.conf    2023-04-02 00:10:25.000000000 -0500
 @@ -52,8 +52,10 @@

.github/scripts/patches/qtbug-111538.diff

@@ -1,3 +1,8 @@
+Description: fix for https://bugreports.qt.io/browse/QTBUG-111538 -
+QDockAreaLayout::updateSeparatorWidgets crash with null pointer dereference
+sometime after restoring state due to recursion into
+QMainWindowLayout::setGeometry causing corruption of separatorWidgets
+
 --- a/src/widgets/widgets/qmainwindowlayout.cpp	2023-02-27 15:50:14.000000000 -0600
 +++ b/src/widgets/widgets/qmainwindowlayout.cpp	2023-02-27 15:50:19.000000000 -0600
 @@ -46,6 +46,8 @@