tools: enforce JS brace style with linting

Enable `brace-style` in ESLint.

Ref: #7094 (comment)
PR-URL: #7630
Reviewed-By: Brian White <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Roman Reiss <[email protected]>
Reviewed-By: Trevor Norris <[email protected]>
Reviewed-By: Rod Vagg <[email protected]>

.eslintrc

@@ -55,6 +55,7 @@ rules:
 
   # Stylistic Issues
   # http://eslint.org/docs/rules/#stylistic-issues
+  brace-style: [2, "1tbs", {allowSingleLine: true}]
   comma-spacing: 2
   eol-last: 2
   indent: [2, 2, {SwitchCase: 1}]