Better `:in_app_module_allow_list` default

[sl0thentr0py]

Currently in_app_module_allow_list defaults to an empty list, so most users don't get good in-app frames marked. Ruby for instance defaults to a combination of project root + known common directory names https://github.com/getsentry/sentry-ruby/blob/c3bcfa0401856d9ee7616c95ab9dfe988a89da30/sentry-ruby/lib/sentry/backtrace.rb#L91-L93