tools: enforce consistent operator linebreak style

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

PR-URL: nodejs#10178
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Roman Reiss <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Jeremiah Senkpiel <[email protected]>
Reviewed-By: Michael Dawson <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Teddy Katz <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>

.eslintrc

@@ -93,6 +93,7 @@ rules:
   no-multiple-empty-lines: [2, {max: 2, maxEOF: 0, maxBOF: 0}]
   no-tabs: 2
   no-trailing-spaces: 2
+  operator-linebreak: [2, after, {overrides: {'?': ignore, ':': ignore}}]
   quotes: [2, single, avoid-escape]
   semi: 2
   semi-spacing: 2