put 2024 under test

We are testing tools and need to maintain a 2024 test directory
so we have added 2024 to `.gitignore` temporarily.

We have added a TODO item to issue #2239 to undo the effect
of this commit and similar testing commits.

.gitignore

@@ -1,5 +1,6 @@
 #
 # sort with: bin/sgi.sh
+2024
 .DS_Store
 /NOTES
 /archive/historic/1984