Update docs and CHANGELOG

Author: znichollscr

changelog/428.docs.md

@@ -0,0 +1 @@
+Added 2026-03-20 IPO email update

docs/forcings-email-archive/SUMMARY.md

@@ -1,4 +1,5 @@
 - [Overview](index.md)
+- [2026-03-20](2026-03-20.md)
 - [2026-02-26](2026-02-26.md)
 - [2026-02-24](2026-02-24.md)
 - [2026-02-16](2026-02-16.md)

docs/forcings-email-archive/index.md

@@ -2,6 +2,7 @@
 
 Here we provide an archive of emails with updates about the forcings sent by the CMIP International Project Office (IPO).
 
+- [2026-03-20](2026-03-20.md)
 - [2026-02-26](2026-02-26.md)
 - [2026-02-24](2026-02-24.md)
 - [2026-02-16](2026-02-16.md)