Scheduler

Features

+ Added a scheduler for asyncio under the import path `scheduler.asyncio.Scheduler`.

Bugfixes

+ The deletion of an unscheduled `Job` with the `scheduler.Scheduler.delete_job` method raised
a `KeyError`. This was corrected and it will now raise a `SchedulerError`.

Misc

+ Refactoring of the internal code structure.
+ New namespace conventions.
+ Revision of the `setup.py` file.
+ Revision of the README.md.
+ Documentation updated.
+ The documentation now uses the [furo](https://github.com/pradyunsg/furo) theme.

Deprecation warnings

+ The `delay` argument used when scheduling jobs of different types will be removed
in a future release.

Known issues

+ Some mypy errors arise due to implementation details regarding the inheritance of the `BaseJob`
and `BaseScheduler`.

Bugfixes

+ Fix the missing lock acquiring in the `JobTimer` described as bug in the
[issue 10](https://gitlab.com/DigonIO/scheduler/-/issues/10).

Misc

+ Fix the version of `mistune` in the `requirement.txt` to prevent pipeline failure
(`m2r2` dependency, not fixed there).

API changes

+ `Scheduler` instanciation and `Scheduler.once` arguments are now keyword only.

Features

+ `Job`s can be given a string alias for identification instead of defaulting to function name.

Misc

+ Python version requirements added to `setup.py`

Misc

+ Revision of the README.md for the first release on PyPI.org

Features

+ `Job`s can be tagged and filtered by sets of string identifiers

API changes

+ `Job`: `params` renamed to `kwargs` and introduced `args` keyword analog to
`sched` library
+ `delete_all_jobs` replaced and implemented within `delete_jobs`
+ `Weekday` implemented as abstract class in `scheduler.trigger.core` instead of
`Enum` in `scheduler.util`. Now with `time` attribute.
+ `Scheduler.once` and `Scheduler.weekly` no longer accept a tuple of `Weekday, datetime.time`
for the timing argument.

Misc

+ `Job` refactoring
+ Documentation updated

API changes

+ Extended `Job` API by `params`, `skip_missing` and `delay`.

Misc

+ Refactoring of `scheduling` functions using `**kwargs`
+ General documentation improvements