fix(demo, docs): update configuration and imports for librawssg 0.5.0

[mroczect]

• Bump librawssg to 0.5.0 in demo Cargo.lock\n- Fix output_dir path and disable generators in demo config\n- Update imports and add context builders in demo main\n- Bump librawssg to 0.5.0 in docs Cargo.lock\n- Update SiteBuilder import and add newline in docs main