Queries should support relative date filters

[schemar]

When I embed a ```tasks block, I want to be able to filter dates also by relative statements.

In addition to, for example, due before 2021-09-12, relative dates could help with a page where I always have certain tasks. That page could look something like the following, as an example:

# Tasks
## Overdue
```tasks
due before today
not done
```

## Due today
```tasks
due on today
not done
```

## Due this week
```tasks
due after today
due before in 8 days
not done
```

[schemar]

Consider an optional dependency on the nldates plugin for obsidian. If tibia installed, the user can use relative dates. If nldates is not installed, then you cannot use relative dates.

🤔

Natural language dates could also already be a dependency due to the rrule dependency which also utilizes nlp.