Add setting to configure increment on numbered list

[yogeshlonkar]

g:mkdx#settings.enter.increment allows to configure how new item index
is increment or decremented in case reorder/ delete

This is useful if you don't want to explicitly number items

[SidOfc]

Hello @yogeshlonkar, cheers for the PR, although I do wonder a bit why this was needed (forgive my potentially naive mindset 😅).

If you don't want to explicitly number list items then you already have the ability to use an unordered list already with - or * tokens. Perhaps I am misunderstanding what this would otherwise achieve though, could you elaborate a little bit more on how it would improve specific use-cases?

[yogeshlonkar]

With this you can create list like

---

1. Something
   1. Random message
   2. Test lines
2. Second component

This list creates above screenshot

Update:
Also if you modify markdown file from different editors you don't have to reorder indexes which I do sometimes. @SidOfc I hope that explains the use case if not I could explain further

[SidOfc]

Hello again Yoge, I understood that the code would end up creating the structure in your first example though I'm not sure how this would allow for the second example since all lists in mkdx are assumed to use one style per list only. e.g. I'm not sure what my code would even do in case of the second example using the mixed numeric / roman numeral style.

That said this seems like a pretty safe feature since it defaults to its original non-configurable value so no harm will really be done here. I added a review comment which will need to be fixed before I merge (it's about adding some missing docs).

Cheers for the PR and apologies for the delays in replies 👍

[SidOfc]

For reference, in above commit you can see what I changed in addition to your additions to the documentation. This PR has been merged 🎉

Cheers for your patience and the contribution 👍

[yogeshlonkar]

@SidOfc thanks