Add optional width prop to embedded side panel component

[rtibbles]

In the image above, you can see the difference when EmbeddedSidePanel is implemented inside and outside FSSP When it's a standalone side panel the width prop, whis is a required prop is passed. When it's inside it has no prop and throws a prop error. My question was, should we add width there or make it an optional prop in EmbeddedSidePanel so it has no error. The width is handled by FSSP when it's the child, and by itself when it's not FSSP's child.

Originally posted by @d0sadata in https://github.com/learningequality/kolibri/issues/9241#issuecomment-1088700938

[marcellamaki]

To resolve this, the width prop in the Embedded Side Panel component should be an option prop. Any uses should be updated so that the width is still displaying correctly in all places, and the prop errors should be resolved in the console after this is implemented.