Add safe versions of various functions from Global.Unsafe.

[nsaunders]

Some concerns about the use of unsafeEncodeURIComponent in purescript-form-urlencoded (and potentially unsafeDecodeURIComponent) were raised in purescript-form-urlencoded#12. Thomas Honeyman suggested that safe alternatives should be added to this library; and, considering #16, it seems like this is something people need.

As I understand, this has been avoided up to now in order to keep purescript-globals a zero-dependency library. I suppose we need to consider whether the benefit of reducing dependency bloat outweighs the cost; which in some cases (as linked above) is error-prone code, and in other cases is opting out of purescript-globals altogether.

If we simply aren't willing to accept dependencies here, I have created a separate purescript-globals-safe library introducing the Global.Safe module that perhaps should be promoted to the purescript or purescript-contrib organizations and published to Pursuit (which I have avoided for now to prevent redundant Global.Safe modules potentially appearing there).

Other than that, I would welcome any feedback you might have, even if this won't be merged, so that I can improve purescript-globals-safe. Thanks in advance!

[garyb]

I would really rather not provide this function. The JSON libraries already have it, and they ensure the accepted type actually is JSON too. A "print a representation of anything" function is ok in purescript-debug, since you can't get a value out of it and all those functions raise a warning, but it's highly dodgy otherwise.

[garyb]

I'd just put these functions in the existing Global module too I think 🙂.

[nsaunders]

Thanks very much for the feedback @garyb. I have updated the pull request accordingly. Please let me know if anything else comes to mind!

[garyb]

Looks great, thanks!