add release notes

Author: LarryRuane

doc/release-notes-22350.md

@@ -0,0 +1,19 @@
+New settings
+------------
+
+- Until now, the `debug.log` file grows without bound until the node
+  is restarted, at which time it is trimmed to 10 MB. Beginning with this
+  release, log rotation is enabled by default. When the `debug.log` file
+  reaches 1 MB, it's renamed to a name that includes the current date and
+  time, such as `debug-2021-06-27T21:19:42Z.log` and `debug.log` is
+  recreated as an empty file. Running `cat` or `grep` with an argument
+  `debug*.log` accesses all debug log files, including the current one
+  (`debug.log`) in time-order. The `-debuglogrotatekeep=n` configuration
+  option specifies the number of rotated debug log files that are retained
+  (default 10). If this value is given as zero, log rotation is disabled
+  (the debug log file is managed as in prior releases). The `-debugloglimit=n`
+  configuration option specifies how large the `debug.log` file must
+  become (in MB) before it is rotated (default is 1). If you specify an
+  alternate debug log file name using `-debuglogfile=path`, the last
+  component of the path must be `debug.log` or else log rotation won't be
+  enabled. (#22350)