Add checkbox based multiselect util component

Takes an array of objects (name, checked, description) and turns it into
a list of checkboxes, one for each element

frontend-reactive/app/components/util/multiselect.hbs

@@ -0,0 +1,13 @@
+<div class={{@wrapper-class}}>
+  {{#each this.args.elements as |element|}}
+    <label class={{@label-class}}>
+      {{element.description}}
+      <Input
+        @type="checkbox"
+        name="{{element.name}}"
+        @checked={{element.checked}}
+        {{on "change" this.onChange}}
+      />
+    </label>
+  {{/each}}
+</div>

frontend-reactive/app/components/util/multiselect.ts

@@ -0,0 +1,21 @@
+import { action } from '@ember/object'
+import Component from '@glimmer/component'
+
+export interface UtilMultiselectSignature {
+  // The arguments accepted by the component
+  Args: {
+    elements: Array<{ name: string; checked: boolean; description: string }>
+  }
+  // Any blocks yielded by the component
+  Blocks: {
+    default: []
+  }
+  // The element to which `...attributes` is applied in the component template
+  Element: null
+}
+
+export default class UtilMultiselect extends Component<UtilMultiselectSignature> {
+  @action onChange() {
+    console.log(this.args.elements)
+  }
+}