Add placeholder text for bio profile text form (#12792)

* Add placeholder text
  * Localize

options/locale/locale_en-US.ini

@@ -426,6 +426,7 @@ uid = Uid
 u2f = Security Keys
 
 public_profile = Public Profile
+biography_placeholder = Tell us a little bit about yourself
 profile_desc = Your email address will be used for notifications and other operations.
 password_username_disabled = Non-local users are not allowed to change their username. Please contact your site administrator for more details.
 full_name = Full Name

templates/user/settings/profile.tmpl

@@ -33,7 +33,7 @@
 				</div>
 				<div class="field {{if .Err_Description}}error{{end}}">
 					<label for="description">{{$.i18n.Tr "user.user_bio"}}</label>
-					<textarea id="description" name="description" rows="2">{{.SignedUser.Description}}</textarea>
+					<textarea id="description" name="description" rows="2" placeholder="{{.i18n.Tr "settings.biography_placeholder"}}">{{.SignedUser.Description}}</textarea>
 				</div>
 				<div class="field {{if .Err_Website}}error{{end}}">
 					<label for="website">{{.i18n.Tr "settings.website"}}</label>