Add placeholder examples to signup form

public/parts/template_person.php

@@ -85,7 +85,7 @@ if (isset($personid) && $database->has('people', ['personid' => $personid])) {
                     "maxlength" => 255,
                     "value" => $personinfo["parentname"],
                     "error" => "Enter the parent or guardian's full name.",
-                    "placeholder" => "Parent McParentson"
+                    "placeholder" => "Parent McParentface"
                 ]
             ]);
         }
@@ -188,7 +188,7 @@ if (isset($personid) && $database->has('people', ['personid' => $personid])) {
                     "maxlength" => 255,
                     "value" => $personinfo["parentname"],
                     "error" => "Enter the parent or guardian's full name.",
-                    "placeholder" => "Guardian McParentson"
+                    "placeholder" => "Parent McParentface"
                 ],
                 [
                     "label" => "Parent Phone",