Simplify installing / running polylint

Install it locally (to avoid version clashes) and then run it with npx (which
finds the locally installed package even when it's not on the path).

Change-Id: I65e35042ae49b9fb0bbe6fd6fba723f8edda8584

package.json

@@ -8,6 +8,7 @@
     "eslint-config-google": "^0.13.0",
     "eslint-plugin-html": "^5.0.5",
     "fried-twinkie": "^0.2.2",
+    "polylint": "^2.10.4",
     "typescript": "^2.x.x",
     "web-component-tester": "^6.5.0"
   },
@@ -15,7 +16,8 @@
     "start": "polygerrit-ui/run-server.sh",
     "test": "WCT_HEADLESS_MODE=1 WCT_ARGS='--verbose -l chrome' ./polygerrit-ui/app/run_test.sh",
     "eslint": "./node_modules/eslint/bin/eslint.js --ignore-pattern 'bower_components/' --ignore-pattern 'gr-linked-text' --ignore-pattern 'scripts/vendor' --ext .html,.js polygerrit-ui/app || exit 0",
-    "test-template": "./polygerrit-ui/app/run_template_test.sh"
+    "test-template": "./polygerrit-ui/app/run_template_test.sh",
+    "polylint": "bazel test polygerrit-ui/app:polylint_test"
   },
   "repository": {
     "type": "git",

polygerrit-ui/README.md

@@ -32,7 +32,6 @@ dependencies can be installed with:
 
 ```sh
 npm install
-sudo npm install -g polylint
 ```
 
 It may complain about a missing `typescript@2.3.4` peer dependency, which is
@@ -175,6 +174,13 @@ To run polylint, execute the following command.
 ```sh
 bazel test //polygerrit-ui/app:polylint_test
 ```
+
+or
+
+```sh
+npm run polylint
+```
+
 ## Template Type Safety
 Polymer elements are not type checked against the element definition, making it
 trivial to break the display when refactoring or moving code. We now run

polygerrit-ui/app/polylint_test.sh

@@ -8,13 +8,13 @@ if [[ -z "$npm_bin" ]]; then
     exit 1
 fi
 
-polylint_bin=$(which polylint)
-if [[ -z "$polylint_bin" ]]; then
-    echo "You must install polylint and its dependencies from NPM."
-    echo "> npm install -g polylint"
+npx_bin=$(which npx)
+if [[ -z "$npx_bin" ]]; then
+    echo "NPX must be on the path."
+    echo "> npm i -g npx"
     exit 1
 fi
 
 unzip -o polygerrit-ui/polygerrit_components.bower_components.zip -d polygerrit-ui/app
 
-${polylint_bin} --root polygerrit-ui/app --input elements/gr-app.html --b 'bower_components'
+npx polylint --root polygerrit-ui/app --input elements/gr-app.html --b 'bower_components' --verbose