Investigate testing of documented examples in CI

[elleryames]

The examples presented in the documentation ( for example Quickstart : Usage : workflow.py ) are intended to be run in CI. However, before this example was fixed it seems that CI was passing.

For this task we should intentionally break one or more examples in docs and test CI.

For example, remove the type information from the example:

# workflow.py

from dewret.tasks import task

@task()
def increment(num):
    return num + 1

[elleryames]

Quality goal but not a blocker for release/0.9.1
FYI: @KamenDimitrov97