Add constantine to important_packages.nim

[mratsim]

This adds Constantine to the important packages. Release announcements:

• https://forum.nim-lang.org/t/11935
• https://github.com/mratsim/constantine/releases/tag/v0.1.0

Unfortunately at the moment I'm in a conundrum.

• Constantine cannot compile on devel due to Semi-regression (?): generic typeclass not matching #23547
• The workaround is changing

  func mulCheckSparse*(a: var QuadraticExt, b: static QuadraticExt) {.inline.} =

  to

  template mulCheckSparse*(a: var QuadraticExt, b: QuadraticExt) =

  but this does not compile on v2.0.8 due to gensym issues despite [backport] fixes #23711; C code contains backtick`gensym  #23716
  .
  i.e. as mentioned in the issue [Semi-regression] C code contains backtick`gensym #23711 there is another gensym bug within templates that was fixed in devel but not the v2.0.x series and that is not fixed by [backport] fixes #23711; C code contains backtick`gensym  #23716

[mratsim]

Following mratsim/constantine#434 it should work on all v1.6.x, v2.0.x and devel

[mratsim]

This is now passing tests, the failure is unrelated (chronos)

[github-actions]

Thanks for your hard work on this PR!
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