UX: Add simple-list setting type (#9970)

app/assets/javascripts/admin/templates/components/simple-list.hbs

@@ -0,0 +1,40 @@
+{{#if collection}}
+  <div class="values">
+    {{#each collection as |value index|}}
+      <div data-index={{index}} class="value">
+        {{d-button
+          action=(action "removeValue")
+          actionParam=value
+          icon="times"
+          class="remove-value-btn btn-small"
+        }}
+
+        {{input
+          title=value
+          value=value
+          class="value-input"
+          focus-out=(action "changeValue" index)
+        }}
+      </div>
+    {{/each}}
+  </div>
+{{/if}}
+
+<div class="simple-list-input">
+  {{input
+    type="text"
+    value=newValue
+    placeholderKey="admin.site_settings.simple_list.add_item"
+    class="add-value-input"
+    autocomplete="discourse"
+    autocorrect="off"
+    autocapitalize="off"}}
+
+  {{d-button
+      action=(action "addValue")
+      actionParam=newValue
+      disabled=inputEmpty
+      icon="plus"
+      class="add-value-btn btn-small"
+    }}
+</div>

app/assets/javascripts/admin/templates/components/site-settings/simple-list.hbs

@@ -0,0 +1,3 @@
+{{simple-list values=value inputDelimiter=inputDelimiter onChange=(action "onChange")}}
+{{setting-validation-message message=validationMessage}}
+<div class="desc">{{html-safe setting.description}}</div>