feat(osmomath): Exp2 function (backport #3708)

[mergify]

This is an automatic backport of pull request #3708 done by Mergify.
Cherry-pick of 89bf606 has failed:

On branch mergify/bp/v13.x/pr-3708
Your branch is up to date with 'origin/v13.x'.

You are currently cherry-picking commit 89bf6068.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   osmomath/exp2.go
	new file:   osmomath/exp2_test.go
	modified:   osmomath/export_test.go
	modified:   scripts/approximations/approximations.py
	modified:   scripts/approximations/main.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[p0mvn]

This depends on #3711 that we aren't backporting