Improve writing of store setters with range and multiple indices

[edemaine]

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Description

Stores have some magic syntax for modifying multiple elements at once: arrays and {from, to, [step]} objects. Previously we called both of them "ranges", but only the latter is ranges. Now the category is "modifying multiple elements", and only one is called a range. I also noticed that the array syntax works for object properties too, so I documented that. Also added a bunch of examples, and added explicit equivalent code to explain exactly what they're doing. Also mentioned the key difference, which is batching.

I didn't actually know these features, but did some basic testing to understand how they work. (The answer is: very generally.)

Related issues & labels

This PR was motivated by zulu's Discord message:

can someone make it clearer that

this in fact mean update at index 1 and 3 and not the range of 1..3

https://docs.solidjs.com/concepts/stores#range-specification

[1,3] is not really a range per say

if the example was [3,10,4] it would have prevented me from making the wrong assumptions

setStore("users", [1, 3], "loggedIn", false)

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