Add Configure Block

This version adds a new StitchTask struct which can be used in replacement of the tuples which were required previously. The old method is still supported, so is entirely backwards compatible.

The new StitchTask struct also supports a new, optional, configuration block. If used, it allows you to mutate the underlying input value before the snapshot is taken for that task. This can be handy if you have functionality not controlled by traits and still want to visualise multiple variants.

Beware though, future stitches using the same value object will use the now mutated version. We would recommend that if you're configuring one task, that you reset/configure every task that uses the same object to prevent inconsistencies and inaccuracies.