update changelog and readme (Metal debug labels)

CHANGELOG.md

@@ -1,5 +1,18 @@
 ## Updates
 
+#### 17-Sep-2023
+
+- The sokol-gfx Metal backend now adds debug labels to Metal resource objects and
+  also passes through the `sg_push/pop_debug_group()` calls. If you use the push/pop
+  debug group calls, please be aware of the following limitations:
+
+  - a push inside a render pass must have an associated pop inside the same render pass
+  - a push outside any render pass must have an associated pop outside any render pass
+  - Metal will ignore any push/pop calls outside render passes (this is because in Metal
+    these are MTLCommandEncoder methods)
+
+  Associated issue: https://github.com/floooh/sokol/issues/889, and PR: https://github.com/floooh/sokol/pull/890.
+
 #### 09-Sep-2023
 
 - a small PR has been merged which fixes a redundant glBindFramebuffer() in the GLES3 backend

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) (**26-Jul-2023** proper image/sampler pair support in sokol_nuklear.h)
+[**See what's new**](https://github.com/floooh/sokol/blob/master/CHANGELOG.md) (**17-Set-2023** debug label support in sokol_gfx.h Metal backend)
 
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