tools: add markdown lint rule for 'Unix'

A recent PR standardized on 'Unix' rather than 'UNIX' or 'unix'. This
change adds a markdown linting rule to enforce it going forward.

PR-URL: #28619
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>
Reviewed-By: Jiawen Geng <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: Trott

tools/lint-md.js

@@ -9,7 +9,7 @@
     "markdown-extensions": "^1.1.1",
     "remark": "^10.0.1",
     "remark-lint": "^6.0.4",
-    "remark-preset-lint-node": "^1.7.0",
+    "remark-preset-lint-node": "^1.8.0",
     "unified-args": "^7.0.0",
     "unified-engine": "^6.0.1"
   },