Add openpgpkey.master-key domain

The WKD setup for master-key.archlinux.org requires this domain to
obtain the master keys via WKD. As WKD falls back to archlinux.org which
contains no .well-known/openpgpkey entry.

tf-stage1/archlinux.tf

@@ -151,10 +151,11 @@ locals {
   #   - value equals the pages verification code
   #
   archlinux_org_gitlab_pages = {
-    "conf"          = "60a06a1c02e42b36c3b4919f4d6de6bf"
-    "whatcanidofor" = "d9e45851002a623e10f6954ff9a85d21"
-    "openpgpkey"    = "7533dfbf3947a5730d9cbcc1e5e63102"
-    "bugs-old"      = "1f3308c8d5763eecb4f9013291aeeac4"
+    "conf"                  = "60a06a1c02e42b36c3b4919f4d6de6bf"
+    "whatcanidofor"         = "d9e45851002a623e10f6954ff9a85d21"
+    "openpgpkey"            = "7533dfbf3947a5730d9cbcc1e5e63102"
+    "openpgpkey.master-key" = "5c7f9c249885c62287dd75d0c1dd99d8"
+    "bugs-old"              = "1f3308c8d5763eecb4f9013291aeeac4"
   }
 
   # This creates archlinux.org TXT DNS entries