Don't check npmjs.com doc links

npmjs.com has taken to blocking such checks with 403 Forbidden.

Author: AArnott

.github/workflows/build.yml

@@ -78,4 +78,4 @@ jobs:
     - name: 🔗 Markup Link Checker (mlc)
       uses: becheran/mlc@18a06b3aa2901ca197de59c8b0b1f54fdba6b3fa # v1.0.0
       with:
-        args: --do-not-warn-for-redirect-to https://learn.microsoft.com*,https://dotnet.microsoft.com/*,https://dev.azure.com/*,https://app.codecov.io/* -p docfx
+        args: --do-not-warn-for-redirect-to https://learn.microsoft.com*,https://dotnet.microsoft.com/*,https://dev.azure.com/*,https://app.codecov.io/* -p docfx -i https://www.npmjs.com/package/*