just a small note: standalone bundle of htm with preact and preact/signals

First of all: thank you very much for this marvelous package!

For my personal needs, however, I "had" to bundle `htm` not only with `preact` but also with `preact/signals` - which surprisingly worked out-of-the-box.

However, I won't open a pull request as this "enhancement" does not add any new functionality but just makes the import a bit more convenient...

Of course, you may close this "issue" whenever you like.