docs(eslint-plugin): add missing ROADMAP link (#998)

packages/eslint-plugin/ROADMAP.md

@@ -603,6 +603,7 @@ Relevant plugins: [`chai-expect-keywords`](https://github.com/gavinaiken/eslint-
 [`@typescript-eslint/no-unused-vars`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unused-vars.md
 [`@typescript-eslint/no-use-before-define`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-use-before-define.md
 [`@typescript-eslint/restrict-plus-operands`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/restrict-plus-operands.md
+[`@typescript-eslint/strict-boolean-expressions`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/strict-boolean-expressions.md
 [`@typescript-eslint/indent`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/indent.md
 [`@typescript-eslint/no-require-imports`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-require-imports.md
 [`@typescript-eslint/array-type`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/array-type.md