docs: update homepage version badge to v0.20

Signed-off-by: Drew Cain <groksrc@gmail.com>

Author: groksrc

content/index.md

@@ -47,7 +47,7 @@ See why your AI needs Basic Memory.
   to: https://basicmemory.com
   variant: outline
   ---
-  v0.19 →
+  v0.20 →
   :::
 
 #default