Optimized images and made small tweaks to GIFs

src/lib/libraries/decks/index.jsx

...ibraries/decks/steps/code-cartoon-01-say-something.en.png

src/lib/libraries/decks/steps/code-cartoon-02-animate.en.gif

...braries/decks/steps/code-cartoon-04-use-minus-sign.en.gif

.../libraries/decks/steps/code-cartoon-05-grow-shrink.en.gif

src/lib/libraries/decks/steps/code-cartoon-07-jump.en.gif

...raries/decks/steps/code-cartoon-10-change-costumes.en.gif

...decks/steps/code-cartoon-11-choose-more-characters.en.jpg