feat(scrollbar): add native scrollbar styles

src/packages/core/src/scrollbar/scrollbar.css

@@ -0,0 +1,12 @@
+._e_scrollbar::-webkit-scrollbar {
+  width: var(--S8);
+}
+
+._e_scrollbar::-webkit-scrollbar-track {
+  background-color: transparent;
+}
+
+._e_scrollbar::-webkit-scrollbar-thumb {
+  border-radius: var(--S4);
+  background-color: var(--N200);
+}

src/packages/core/src/scrollbar/scrollbar.html

@@ -0,0 +1,7 @@
+<div class="_e_scrollbar" style="height: 200px; overflow-y: scroll; font: var(--Body1);">
+  <p>A male hummingbird simply pausing on a perch can mesmerize us with his colorful, iridescent plumage. But it turns out we humans are likely missing the full effect—because hummingbirds see colors that humans cannot detect, a new study says.</p>
+  <p>Scientists have long known that birds probably have better color vision than humans do. Like most primates, humans are trichromatic—that is, our eyes have three types of color-sensitive receptors or cones: blue, green, and red. But birds have four color cones, meaning they are tetrachromatic.</p>
+  <p>With our three color cones, we can see the colors of the rainbow—red, orange, yellow, green, blue, indigo, and violet—the so-called spectral hues. We can also see one pure nonspectral (meaning, not in the rainbow) color, purple, because it stimulates our red and blue cones simultaneously.</p>
+  <p>Birds’ four color cones theoretically let them discriminate a broader range of colors, including the ultraviolet spectrum, which includes colors such as UV-green and UV-red. But so far, researchers have made few investigations into what birds can actually see. (Explore our interactive on the science of hummingbirds.)</p>
+  <p>Then Mary Stoddard, a Princeton University evolutionary biologist, and colleagues carried out a series of field experiments with wild broad-tailed hummingbirds near the Rocky Mountain Biological Laboratory in Colorado. The remarkable results revealed the birds could discern spectral-colored feeders from feeders in nonspectral colors.</p>
+</div>

src/packages/core/src/scrollbar/scrollbar.stories.mdx

@@ -0,0 +1,14 @@
+import { Meta, Preview, Story } from '@storybook/addon-docs/blocks';
+import pretty from 'pretty';
+
+import scrollbar from './scrollbar.html';
+
+<Meta title='Core/Scrollbar' />
+
+# Modal
+
+<Preview>
+  <Story name="default" height="240px" parameters={{ docs: { source: { code: pretty(scrollbar) } } }}>
+    { () => scrollbar }
+  </Story>
+</Preview>