binds are creating an iframe limiting per column styling.

[Farro178]

Hey!

I just wanna start off by saying you've got a really nice simple library here, i'm using a slightly adapted version for my own needs with more of a focus on explicitly defining the amount of columns.

bind:clientWidth={masonryWidth}
bind:clientHeight={masonryHeight}

One thing I noticed was the bind is creating an Iframe in the DOM (maybe this is an expected behaviour in Svelte, i'm still pretty new to it). As i'm not using it I could just remove it but perhaps it's something that could be improved down the line. As this currently stops you from applying classes to specific columns for example in my use-case i'm adding a margin-top to every 2nd child.