npm-doctor: add page (#14262)

* npm-doctor: add page

* Update description and url

---------

Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>

pages/common/npm-doctor.md

@@ -0,0 +1,24 @@
+# npm doctor
+
+> Check the health of the npm environment.
+> More information: <https://docs.npmjs.com/cli/commands/npm-doctor>.
+
+- Run all default health checks for npm:
+
+`npm doctor`
+
+- Check the connection to the npm registry:
+
+`npm doctor connection`
+
+- Check the versions of Node.js and npm in use:
+
+`npm doctor versions`
+
+- Check for permissions issues with npm directories and cache:
+
+`npm doctor permissions`
+
+- Validate the cached package files and checksums:
+
+`npm doctor cache`