TechDocs: show outdated docs and asnyc build new

Signed-off-by: Chongyang Adrian, Ke <ftt.adrian.ke@grabtaxi.com>

plugins/techdocs/package.json

@@ -38,10 +38,10 @@
     "@backstage/test-utils": "^0.1.9",
     "@backstage/theme": "^0.2.4",
     "@backstage/techdocs-common": "^0.4.5",
+    "@backstage/errors": "^0.1.1",
     "@material-ui/core": "^4.11.0",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",
-    "@types/react": "^16.9",
     "react": "^16.13.1",
     "react-dom": "^16.13.1",
     "react-router": "6.0.0-beta.0",
@@ -56,8 +56,10 @@
     "@testing-library/jest-dom": "^5.10.1",
     "@testing-library/react": "^11.2.5",
     "@testing-library/user-event": "^12.0.7",
+    "@types/react": "^16.9",
     "@types/jest": "^26.0.7",
     "@types/node": "^14.14.32",
+    "@types/react": "^16.9",
     "canvas": "^2.6.1",
     "cross-fetch": "^3.0.6",
     "msw": "^0.21.2"