[Web] Add sieve template, thanks to @Programmierus

data/web/inc/presets/sieve/sieve_8.yml

@@ -0,0 +1,11 @@
+headline: lang.sieve_preset_8
+content: |
+  require "envelope";
+  require "variables";
+  if allof (
+    envelope :all :matches "to" "*",
+    not header :contains "To" "${1}",
+    address :is "From" "${1}"
+  ) {
+    discard;
+  }