Preparing for v2.3

[manodeep]

• Will include avx512
• Additional optimizations based on min. separations between cell-pairs

[astropy-bot[bot]]

Hi there @manodeep :wave: - thanks for the pull request! I'm just a friendly :robot: that checks for issues related to the changelog and making sure that this pull request is milestoned and labeled correctly. This is mainly intended for the maintainers, so if you are not a maintainer you can ignore this, and a maintainer will let you know if any action is required on your part :smiley:.

Everything looks good from my point of view! :+1:

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[manodeep]

@lgarrison I will merge this PR in for now but we will need a proper review once this branch is ready to merge into master