Add constantine to important_packages.nim (#23801)

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
#23547
- The workaround is changing 
  ```Nim
func mulCheckSparse*(a: var QuadraticExt, b: static QuadraticExt)
{.inline.} =
  ```
  to
  ```Nim
  template mulCheckSparse*(a: var QuadraticExt, b: QuadraticExt) =
  ```
but this does not compile on v2.0.8 due to `gensym` issues despite
#23716

![image](https://github.com/nim-lang/Nim/assets/22738317/21c875d7-512f-4c21-8547-d12534e93a58).
i.e. as mentioned in the issue
#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 #23716

testament/important_packages.nim

@@ -58,6 +58,7 @@ pkg "cligen", "nim c --path:. -r cligen.nim"
 pkg "combparser", "nimble test --mm:orc"
 pkg "compactdict"
 pkg "comprehension", "nimble test", "https://github.com/alehander92/comprehension"
+pkg "constantine", "nimble make_lib"
 pkg "cowstrings"
 pkg "criterion", allowFailure = true # needs testing binary
 pkg "datamancer"