remove spellcheck (requires node 20)

Author: HUSSAR-mtrela

.markdownlint-README.md

@@ -6,7 +6,10 @@ This directory contains markdown linting configuration for the Ignite UI for Ang
 
 ## TODO
 
-add devDependencies "markdownlint-cli": "^0.45.0",
+Add devDependencies:
+
+- "markdownlint-cli": "^0.45.0",
+- "cspell": "^9.2.2",
 
 ## Rules Configuration