mention mouse button modifiers in changelog and readme

CHANGELOG.md

@@ -1,5 +1,13 @@
 ## Updates
 
+- **12-Apr-2021**: Minor new feature in sokol_app.h: mouse buttons are now
+  also reported as modifier flags in most input events (similar to the
+  Ctrl-, Alt-, Shift- and Super-key modifiers). This lets you quickly check
+  what mouse buttons are currently pressed in any input event without having
+  to keep track of pressed mouse buttons yourself. This is implemented in the following
+  sokol_app.h backends: Win32, UWP, Emscripten, X11 and macOS. Example
+  code is in the [events-sapp.cc](https://floooh.github.io/sokol-html5/events-sapp.html) sample
+
 - **10-Apr-2021**: followup fixes from yesterday: custom icon support on macOS
   has been added (since macOS has no regular window icons, the dock icon is
   updated instead), and a bugfix in the internal helper which select the

README.md

@@ -6,7 +6,7 @@ Simple
 [STB-style](https://github.com/nothings/stb/blob/master/docs/stb_howto.txt)
 cross-platform libraries for C and C++, written in C.
 
-[**See what's new**](https://github.com/floooh/sokol/blob/master/CHANGELOG.md) (**09-Apr-2021** window icon support in sokol_app.h)
+[**See what's new**](https://github.com/floooh/sokol/blob/master/CHANGELOG.md) (**12-Apr-2021** mouse button modifiers in sokol_app.h input events)
 
 ## Examples and Related Projects