Publish `TimeFormat` as a separate module

[dolmen]

I find that the TimeFormat type (and its constants) is useful with any SQLite Go driver, not just yours.

What about publishing it as a separate module?

[ncruces]

That's a good point. There are various bits of this project that would be useful regardless of the used driver/binding. I will consider giving them a home.

Meanwhile, feel free to copy whatever bits you need into your project.