chore: bump lint to support optional chaining (#4905)

package.json

@@ -73,7 +73,7 @@
     "@types/jest": "^24.0.16",
     "@vant/cli": "^1.0.6",
     "@vant/doc": "^2.5.7",
-    "@vant/eslint-config": "^1.3.0",
+    "@vant/eslint-config": "^1.4.0",
     "@vant/markdown-loader": "^2.2.0",
     "@vant/markdown-vetur": "^1.0.0",
     "@vant/touch-emulator": "^1.1.0",
@@ -87,7 +87,7 @@
     "css-loader": "^3.1.0",
     "csso": "^3.5.1",
     "dependency-tree": "^7.0.2",
-    "eslint": "^6.1.0",
+    "eslint": "^6.6.0",
     "fast-glob": "^3.0.4",
     "gh-pages": "2.0.1",
     "html-webpack-plugin": "3.2.0",