Upgraded `to-map()` with warnings, support for zero-based indexing & more

[lolmaus]

Hey Hugo. ^_^

I stumbled upon this and noticed that it lacks the @each loop.

Then i noticed that the example requires an index variable.

Then i remembered having solved this case before.

Then i decided to have a look whether your SassyLists has this function and didn't find one.

So i created one for you.

But before submitting a pull request i decided to have a look into your roadmap and found that the function is already implemented in the next branch.

But my implementation seemed better to me, so i decided to send the pull request anyway.

Don't hesitate to decline it if you feel so.

PS I've tested it on SassMeister and it seems to work, but i didn't use this very code in any project. Looks like i've got a suggestion for your roadmap.

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Upgraded to-map():

• Added warnings against illegal arguments.
• Added optional parameter that allows indexing the resulting map starting with any number, e. g. zero.
• Added an alias enumerate, which is how Python folk refer to this feature.
• Expanded the description with my favorite use case:

@each $i, $value in enumerate($list)

[KittyGiraudel]

Manually merged into 2.0-beta. Thanks Andrey!

[lolmaus]

My pleasure.