Bump pack version after release.
diff --git a/ARM.CMSIS.pdsc b/ARM.CMSIS.pdsc
index 8734bc3..2d3d618 100644
--- a/ARM.CMSIS.pdsc
+++ b/ARM.CMSIS.pdsc
@@ -8,6 +8,9 @@
   <url>http://www.keil.com/pack/</url>
 
   <releases>
+    <release version="5.8.1">
+      Active development ...
+    </release>
     <release version="5.8.0" date="2021-06-24">
       CMSIS-Core(M): 5.5.0 (see revision history for details)
         - Updated GCC LinkerDescription, GCC Assembler startup