moved some widgets to elements

packages/web/src/elements/DropDownButton.svelte

@@ -0,0 +1,22 @@
+<script lang="ts">
+  import _ from 'lodash';
+
+  import FontIcon from '../icons/FontIcon.svelte';
+  import { currentDropDownMenu } from '../stores';
+  import InlineButton from './InlineButton.svelte';
+
+  export let icon = 'icon chevron-down';
+  export let menu;
+  let domButton;
+
+  function handleClick() {
+    const rect = domButton.getBoundingClientRect();
+    const left = rect.left;
+    const top = rect.bottom;
+    currentDropDownMenu.set({ left, top, items: _.isFunction(menu) ? menu() : menu });
+  }
+</script>
+
+<InlineButton square on:click={handleClick} bind:this={domButton}>
+  <FontIcon {icon} />
+</InlineButton>