Remove width constraint, add overflow-x scroll

[Wutras]

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[Wutras]

This should fix #22.
Tested locally with very wide content and worked properly.
There's a visual bug with the time element, but that's not really important. position: sticky and similar solutions don't work as a trivial fix because of the overflow-x: scroll. I'll try finding a better solution in the future, possibly styling various messages slightly differently or adding another container which handles the overflow (preferred).