Widen the range of default_dependency_paths

Reloader treats shared/**/*.rb  as monitored, but the loader hasn't loaded it
see https://github.com/padrino/padrino-framework/blob/1b5b0716d75d6e6ca9c1d523caa7016713ea7fcc/padrino-core/lib/padrino-core/reloader.rb#L224

/cc @ujifgc @padrino/core-members