Большое —
в деталях.

<SiteLayout>
  <Header navigation={navigation} />
  <main>{children}</main>
  <Footer contacts={contacts} />
</SiteLayout>

const visible = projects.filter(
  project => category === 'Все'
    || project.category === category
);

return visible.map(project => (
  <ProjectCard key={project.id}
    project={project} />
));