add info about KDE patches

Author: kambala-decapitator

conan_patches/qt/patches/_kde.md

@@ -0,0 +1,5 @@
+Patches from [KDE project](https://community.kde.org/Qt5PatchCollection) were generated from a72077a88903fe532f6a749677eb4da4ea99f79f, but a few had to be dropped because Conan can't apply them, namely:
+
+- 0018-Fix-memory-leak
+- 0024-Use-icon-themes-in-QPrintPreviewDialog-if-they-exist
+- 0061-Annotate-QMutex-with-TSAN-annotations