tools: enforce consistent operator linebreak style

Adds the `operator-linebreak` rule to our ESLint config.

PR-URL: https://github.com/nodejs/node/pull/10178
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

.eslintrc

@@ -65,6 +65,7 @@ rules:
   no-mixed-spaces-and-tabs: 2
   no-multiple-empty-lines: [2, {max: 2}]
   no-trailing-spaces: 2
+  operator-linebreak: [2, after, {overrides: {'?': ignore, ':': ignore}}]
   quotes: [2, "single", "avoid-escape"]
   semi: 2
   space-before-blocks: [2, "always"]