Add a way to get the bot version via Delta Chat for bug reporting

[link2xt]

When the bot is deployed, it would be nice to have a way to get the bot version for bugreports.

E.g. when building the bot with the scripts/dist.sh script, put the git tag/commit into a file in the bot assets (bot-data) that the bot can read and reply with when user sends a /version command, or include the version in webxdc updates for the frontend to display in the footer.

[Septias]

Using the tarball should not be the only option to run the bot imo.
Maybe the bot could actually use git cli to find out the commit/tag.

[link2xt]

There is anyway a build process: building the bot binary and assets (frontend .xdcs). Version file is an asset just the same way as .xdcs and can be created during the build process.

[adbenitez]

ideally the CLI should have a --version option to check version, and the webxdc store should also have some version tag somewhere, maybe in an "About" section where then we can also explain to devs how to submit their apps

[link2xt]

ideally the CLI should have a --version option to check version

This issue is about being able to check the version from the user side, not from the admin side when you have SSH access. --version option or version subcommand does not help with this because the user can only interact with the bot via email messages.

I opened a separate issue: #50