Optimize .png images

src/lib/libraries/decks/steps/add-backdrop.en.png

src/lib/libraries/decks/steps/add-effects.en.png

src/lib/libraries/decks/steps/change-size.en.png

src/lib/libraries/decks/steps/fly-select-flyer.en.jpg

.../libraries/decks/steps/glide-around-back-and-forth.en.png

src/lib/libraries/decks/steps/glide-around-point.en.png

src/lib/libraries/decks/steps/hide-show.en.png

src/lib/libraries/decks/steps/imagine-change-costumes.en.png

...raries/decks/steps/imagine-choose-another-backdrop.en.png

...ibraries/decks/steps/imagine-choose-another-sprite.en.png

...ib/libraries/decks/steps/imagine-choose-any-sprite.en.png

src/lib/libraries/decks/steps/imagine-choose-backdrop.en.png

src/lib/libraries/decks/steps/imagine-choose-sound.en.png

...lib/libraries/decks/steps/imagine-click-green-flag.en.png

src/lib/libraries/decks/steps/imagine-fly-around.en.png

src/lib/libraries/decks/steps/imagine-glide-to-point.en.png

src/lib/libraries/decks/steps/imagine-grow-shrink.en.png

src/lib/libraries/decks/steps/imagine-left-right.en.png

...b/libraries/decks/steps/imagine-type-what-you-want.en.png

src/lib/libraries/decks/steps/imagine-up-down.en.png