Add release notes for Splinter 0.5.26
# Release Notes
+## Changes in Splinter 0.5.26
+
+### Highlights
+
+* Stabilized the splinterd feature `"log-config"`. This feature allows for
+ finer-grained configuration of the log output.
+
+### splinter CLI
+
+* Add `--group` option to the `splinter keygen` subcommand. This option allows
+ the user to modify the group of the resulting key files, or automatically set
+ the group based on the target directory. The group now defaults to the user's
+ group if this option is omitted.
+
+### splinterd
+
+* Stabilize `"log-config"` feature by removing it. The fine-grained log
+ configuration is now available by default.
+
## Changes in Splinter 0.5.25
### Highlights
