alert formatting

[spaette]

@aplavin

I note you rewrote some of the markdown text in your previous commit.

Were the Maintainers inclined to use alert formatting here are a few examples.

docs/src/counterintuitive.md

!!! note
    This behavior only arises for *mutable* `struct`s. If `Foo` were immutable, re-assigning the `b` field would be an error, and there would be no opportunity for confusion. Moreover, the performance of immutable struct creation is generally much better than for mutable structs. Thus, it is recommended to use immutable structs with StructArray whenever possible.

> [!NOTE]
> This behavior only arises for *mutable* `struct`s. If `Foo` were immutable, re-assigning the `b` field would be an error, and there would be no opportunity for confusion. Moreover, the performance of immutable struct creation is generally much better than for mutable structs. Thus, it is recommended to use immutable structs with StructArray whenever possible.

docs/src/index.md

!!! warning
    Unlike the other cases above, `soa` contains a *copy* of the data in `aos`. For more discussion, see [Some counterintuitive behaviors](@ref).

> [!CAUTION]
> Unlike the other cases above, `soa` contains a *copy* of the data in `aos`. For more discussion, see [Some counterintuitive behaviors](@ref).

> [!IMPORTANT]
> Unlike the other cases above, `soa` contains a *copy* of the data in `aos`. For more discussion, see [Some counterintuitive behaviors](@ref).

> [!WARNING]
> Unlike the other cases above, `soa` contains a *copy* of the data in `aos`. For more discussion, see [Some counterintuitive behaviors](@ref).