[Feature Request] Allow triggering updates

[HarelM]

Hi, and thanks for this great tool!

Currently, as far as I understand from the docs, there's no way to trigger updates on demand/manually.

We are looking into running this tool on a server that might have memory constraints, and thus we want to be able to control when the update runs in order to make sure nothing runs at the same time and generally better control when things run and what is running.

To do so, we'll need to be able to trigger the update on demand (using some docker run with different entry point or some other way).

If this is already supported this is great, but I haven't found documentation of this option, nor a way to completely avoid updates as part of the ENV args.

If I'm missing anything do let me know and I'll be happy to submit a PR to update the docs.

Thanks again for all the hard work invested in this!

[HarelM]

Looking at the code might it be possible to do it by setting:
OVERPASS_DIFF_URL to an empty string so that updates will not run, and manually triggering update_overpass.sh script by setting it as the entry point of the container and giving it the relevant environment args?

Let me know if I'm on the right direction.