fix: serve local assets in development server

[BadMannersXYZ]

Closes #75

[shishkin]

Now when I think about it again, I don't think it would be a good idea to serve images through this integration in dev. A better approach to resolve build/dev discrepancy would be to not rely on static build in dev and manually populate pagefind index in dev mode. Especially now, when we use pagefind JS API to build the index. However, I don't have enough knowledge of astro and vite internals to understand how to get pages content in dev.