Add HTML autocomplete attributes for passwords

These are recommended to help browsers and password managers figure out
how to autofill. As explained in this blog post:
https://hacks.mozilla.org/2019/10/firefox-70-a-bountiful-release-for-all/

tildes/tildes/templates/register.jinja2

@@ -32,12 +32,12 @@
 
     <div class="form-group">
       <label class="form-label" for="password">Password</label>
-      <input class="form-input" id="password" name="password" type="password" placeholder="Password">
+      <input class="form-input" id="password" name="password" type="password" placeholder="Password" autocomplete="new-password">
     </div>
 
     <div class="form-group">
       <label class="form-label" for="password_confirm">Confirm password</label>
-      <input class="form-input" id="password_confirm" name="password_confirm" type="password" placeholder="Confirm password">
+      <input class="form-input" id="password_confirm" name="password_confirm" type="password" placeholder="Confirm password" autocomplete="new-password">
     </div>
 
     <div class="form-group">

tildes/tildes/templates/settings_password_change.jinja2

@@ -18,17 +18,17 @@
 
   <div class="form-group">
     <label class="form-label" for="old_password">Current password</label>
-    <input class="form-input" id="old_password" name="old_password" type="password" placeholder="Current password">
+    <input class="form-input" id="old_password" name="old_password" type="password" placeholder="Current password" autocomplete="current-password">
   </div>
 
   <div class="form-group">
     <label class="form-label" for="new_password">New password</label>
-    <input class="form-input" id="new_password" name="new_password" type="password" placeholder="New password">
+    <input class="form-input" id="new_password" name="new_password" type="password" placeholder="New password" autocomplete="new-password">
   </div>
 
   <div class="form-group">
     <label class="form-label" for="new_password_confirm">Confirm new password</label>
-    <input class="form-input" id="new_password_confirm" name="new_password_confirm" type="password" placeholder="Confirm new password">
+    <input class="form-input" id="new_password_confirm" name="new_password_confirm" type="password" placeholder="Confirm new password" autocomplete="new-password">
   </div>
 
   <div class="form-buttons">