P5 component prop project just gets overwritten on instance init

[tonyketcham]

Describe the bug
Passing in a p5 instance to the project prop does nothing and just gets overwritten when the p5 sketch initializes:

<P5 {sketch} {project} />

It should be made private to the P5.svelte component and an experiment on feature/linked-instances may lead to a future PR introducing the ability to create multiple viewports of the same sketch via passing around a p5 project, presuming that is supported in p5's instance mode.

[tonyketcham]

Fixing this will lead to a niche & mild breaking change which shouldn't actually break any sketches themselves but could break CI where users have eslint or svelte-check jobs that detect an attempt to pass to a non-existant prop