feat(component): add FileUploader

Closes #16

src/components/FileUploader/FileUploaderItem.svelte

@@ -0,0 +1,49 @@
+<script>
+  let className = undefined;
+  export { className as class };
+  export let id = Math.random();
+  export let status = 'uploading';
+  export let iconDescription = '';
+  export let name = '';
+  export let invalid = false;
+  export let errorSubject = '';
+  export let errorBody = '';
+  export let style = undefined;
+
+  import { createEventDispatcher } from 'svelte';
+  import { cx } from '../../lib';
+  import Filename from './Filename.svelte';
+
+  const dispatch = createEventDispatcher();
+  const _class = cx(
+    '--file__selected-file',
+    invalid && '--file__selected-file--invalid',
+    className
+  );
+</script>
+
+<span on:mouseover on:mouseenter on:mouseleave class={_class} {style}>
+  <p class={cx('--file-filename')}>{name}</p>
+  <span class={cx('--file__state-container')}>
+    <Filename
+      {iconDescription}
+      {status}
+      {invalid}
+      on:keydown={({ key }) => {
+        if (key === ' ' || key === 'Enter') {
+          dispatch('delete', id);
+        }
+      }}
+      on:click={() => {
+        dispatch('delete', id);
+      }} />
+  </span>
+  {#if invalid && errorSubject}
+    <div class={cx('--form-requirement')}>
+      <div class={cx('--form-requirement__title')}>{errorSubject}</div>
+      {#if errorBody}
+        <p class={cx('--form-requirement__supplement')}>{errorBody}</p>
+      {/if}
+    </div>
+  {/if}
+</span>