refactor(pollingset): make bad state impossible

[Hweinstock]

Problem

Right now PollingSet exposes both the add and the start methods. The start adds the item and starts the timer, while the add only adds the item.

This allows a consumer to create a non-empty PollingSet where the timer never started.

Solution

• Overwrite the add method so that a consumer is forced to start the timer when adding items.

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[justinmk3]

Nice!

[justinmk3]

Overwrite the add method so that a consumer is forced to start the timer when adding items.

it's only overriding, right? "overwrite" makes me think of this.add = () => { ... } :)