Actually, no idea why but it works on my test repo with the same code,
but on the actual nerdlog repo it complains about not having the
libx11-dev.

It's not just a proof of concept anymore.

To make it possible to build Nerdlog as a Debian package, see
#41 for details.

Also, add support for the `NERDLOG_NO_CLIPBOARD` env var: if it's set,
clipboard will be disabled. Needed for tests to avoid having the "Copy"
button in the UI on all platforms. Let it remain an undocumented feature
for now.

In particular, mention the `adm` and `systemd-journal` groups there.

E.g. if `--time 'invalid-time'` was given, Nerdlog used to just panic,
now it prints a slightly better error message.

Which can be used for setting nerdlog options, using the same syntax as
the `:set` command, so e.g. `--set numlines=1000`.

It provides some mitigation for not yet having a persistent config file,
which requires more thought if we want it to be a script and not just a
config file.

It'll be useful even when we have the config file as well though, since
it will take precedence over options in the config file. In particular
it will likely be used in tests.

There was code to generate better histogram data in a corner case when
the timestamp decreases, but unfortunately it broke a very common case
when the timestamps are going from May to Jun.

So this commit disables the corner-case handling for now (until we have
a better solution), in order to fix the May to Jun transition.

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>