Document nvim-lspconfig integration

[peytondmurray]

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Summary

This PR adds a note in the documentation about nvim-lspconfig integration, merged in neovim/nvim-lspconfig#4382.

Here's what the relevant section of the docs looks like when rendered:

Closes #1916.

Please note that these changes haven't yet been released upstream in nvim-lspconfig, but can be found on the master branch there. If it would be better to wait for a release, I can move this back into draft and reopen at the next release.

[woodruffw]

Thanks @peytondmurray, LGTM!

I'm personally fine with landing these docs before a nvim-lspconfig release, particularly if the release is expected to be somewhat soon. Do you happen to have a sense for that?

[woodruffw]

Based on the previous release cadence it looks reasonably fast, so I'm merging.

[woodruffw]

Thanks again @peytondmurray!

[peytondmurray]

No worries, it looks like roughly a month or two between releases, so it won't be a long wait :)