chore: add demo (#1319)

* fix: 修复 featureScale 错误

* style: lint style

* fix: remove featureScalePlugin async

* chore: add demo

* style: lint style

Co-authored-by: shihui <yiqianyao.yqy@alibaba-inc.com>

dev-demos/features/line/lineblur.md

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+### Line Blur
+<code src="./lineblur.tsx"></code>

dev-demos/features/line/lineblur.tsx

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+import { LineLayer, Scene } from '@antv/l7';
+import { GaodeMap } from '@antv/l7-maps';
+import React, { useEffect } from 'react';
+
+export default () => {
+  useEffect(() => {
+    const scene = new Scene({
+      id: 'map',
+      map: new GaodeMap({
+        center: [122, 28],
+        zoom: 5,
+        style: 'dark',
+      }),
+    });
+
+    fetch(
+      'https://gw.alipayobjects.com/os/bmw-prod/55304d8d-4cb0-49e0-9d95-9eeacbe1c80a.json',
+    )
+      .then((res) => res.json())
+      .then((data) => {
+        const blurLine = new LineLayer()
+          .source(data)
+          .size(5)
+          .style({
+            opacity: 0.8,
+            sourceColor: '#f00',
+            targetColor: '#ff0',
+            linearDir: 'horizontal',
+          });
+        scene.addLayer(blurLine);
+      });
+  }, []);
+  return (
+    <div
+      id="map"
+      style={{
+        height: '500px',
+        position: 'relative',
+      }}
+    />
+  );
+};