Extract TrendLine from Lighthouse plugin (#532)

* Extract TrendLine from Lighthouse plugin

* Create TrendLine.stories.tsx

* Change lifecycle names

* Made story example smaller

* Review comment

* Update TrendLine.tsx

plugins/lighthouse/package.json

@@ -13,8 +13,7 @@
     "clean": "backstage-cli clean"
   },
   "dependencies": {
-    "react-markdown": "^4.3.1",
-    "react-sparklines": "^1.7.0"
+    "react-markdown": "^4.3.1"
   },
   "devDependencies": {
     "@backstage/cli": "^0.1.1-alpha.4",
@@ -29,7 +28,6 @@
     "@testing-library/user-event": "^7.1.2",
     "@types/jest": "^24.0.0",
     "@types/node": "^12.0.0",
-    "@types/react-sparklines": "^1.7.0",
     "@types/testing-library__jest-dom": "5.0.2",
     "jest-fetch-mock": "^3.0.3",
     "react": "^16.13.1",