patch 8.2.3022: available encryption methods are not strong enough

Problem:    Available encryption methods are not strong enough.
Solution:   Add initial support for xchaha20. (Christian Brabandt,
            closes #8394)
diff --git a/runtime/doc/various.txt b/runtime/doc/various.txt
index eb45922..0ad12e8 100644
--- a/runtime/doc/various.txt
+++ b/runtime/doc/various.txt
@@ -444,6 +444,7 @@
 T  *+scrollbind*	|'scrollbind'|
 B  *+signs*		|:sign|
 N  *+smartindent*	|'smartindent'|
+B  *+sodium*		compiled with libsodium for better encryption support
 B  *+sound*		|sound_playevent()|, |sound_playfile()| functions, etc.
 N  *+spell*		spell checking support, see |spell|
 N  *+startuptime*	|--startuptime| argument