Add more TODOs for cmake migration

TODO.md

diff --git a/TODO.md b/TODO.md
index a68aeff..1f48466 100644
--- a/TODO.md
+++ b/TODO.md
@@ -11,7 +11,13 @@
   - replace `make distcheck`
   - cmake on Linux: man pages not built (https://github.com/nih-at/libzip/issues/8)
   - check generated xcode project
-  
+  - add custom targets:
+    - mkman (mdoc -> man)
+    - handle_links (one man page for multiple functions)
+    - update-errors (zip.h -> zip_errors.mdoc)
+    - regress zip.zip -> zip
+    - regress clean up sandboxes
+
 * clone support
   - APFS
   - `zip_source_buffer`: also support multiple buffers, compare `writev` `struct iovec`