Upgrade to Nextra latest (3 or 4 )

[ganeshpatil386386]

Since the SWR website is built using Nextra, it is still running on an older version. Recently, Nextra released Nextra 4 with MDX v3 support.

You can check here that we are still using Nextra 2. It would be beneficial to upgrade to at least Nextra 3 to take advantage of the latest features.

[huozhi]

PR is welcomed!

[ganeshpatil386386]

Thanks @huozhi
Working on it!