update CHANGELOG and README for Emscripten 3.21 fixes

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## Updates
 
+- **10-Sep-2022**: sokol_app.h and sokol_args.h has been fixed for Emscripten 3.21, those headers
+  used the Emscripten Javascript helper function ```ccall()``` which is now part of the
+  'legacy runtime' and causes linker errors. Instead of ```ccall()``` sokol_app.h and sokol_args.h
+  now drop down to a lower level set of Emscripten JS helper functions (which hopefully won't
+  go away anytime soon).
+
 - **05-Aug-2022**: New officially supported and automatically updated language bindings for Odin:
   https://github.com/floooh/sokol-odin (also see [gen_odin.py](https://github.com/floooh/sokol/blob/master/bindgen/gen_odin.py))
 

README.md

@@ -4,7 +4,7 @@ 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) (**10-Jul-2022** sokol_app.h can now set the mouse cursor type, and assorted changes)
+[**See what's new**](https://github.com/floooh/sokol/blob/master/CHANGELOG.md) (**10-Sep-2022** an important compatibility fix for Emscripten 3.21 in sokol_app.h and sokol_args.h)
 
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