Adding documentation for Nekrs application on Polaris

[uumesh]

Adding documentation for building and running Nekrs application on Polaris - modules, build instructions, and run scripts

[felker]

I will take a look in more detail later @uumesh. Where in the sidebar will the page be linked? You'll need to edit https://github.com/argonne-lcf/user-guides/blob/main/mkdocs.yml accordingly

[uumesh]

Thanks for the note, @felker. I have added the link to the page in the mkdocs.yml file.