Add `runAt` to an example

[Miserlou]

Took me a little digging to figure out why my scripts took so long to run, I had to change the runAt value for browser.tabs.executeScript. It'd be useful if these examples could have an example that included runAt.

[wbamberg]

It's a good idea. Do you have an idea of something that might work as a simple illustrative example?

[Miserlou]

I use it for Poop, so maybe anything which needs to interact with content immediately rather than waiting for a complete pageload, for instance a content-blocker which updates a counter on the page or something like that.

[rebloor]

No activity within the last three years, closing.