parser: for loop

[cooper]

for [@variable] {
    Some formatted text and/or block content to repeat.
    If @variable is a list, you can access each item with the special variable [@value].
    If @variable is an object, you can access the [@key] and [@value] of the pair with these two special variables.
    In either case, [.property] is shorthand for [@value.property].
}

[cooper]

It should also support assigning your own var in case you want to nest loops and access an outer value

for [@variable as @item] {
}

[cooper]

does this need to be implemented in the parser? maybe it could be implemented as a block type.