Add effect buttons and tests for the component

src/components/icon-button/icon-button.css

src/components/sound-editor/icon--echo.svg

src/components/sound-editor/icon--higher.svg

src/components/sound-editor/icon--louder.svg

src/components/sound-editor/icon--lower.svg

src/components/sound-editor/icon--reverse.svg

src/components/sound-editor/icon--robot.svg

src/components/sound-editor/icon--softer.svg

src/components/sound-editor/sound-editor.css

src/components/sound-editor/sound-editor.jsx

src/containers/sound-editor.jsx

.../unit/components/__snapshots__/sound-editor.test.jsx.snap

test/unit/components/sound-editor.test.jsx

test/unit/containers/sound-editor.test.jsx