fix: screenplay not loaded when importing txt or clap

[devniel]

Hi,

The useEffect with getClap was not detecting changes, refactoring it to use meta is a simple fix but I think a better approach is to fill the proper store when setting timeline.setClap() to avoid complications with useEffect apart of avoiding additional renders. An even better approach could be to have a global store where to proxy calls to TimelineStore and ScriptEditorStore via a unique setClap, I think we could do that in the future.