Document entitlement / plist norms

Currently when you create a new app you have to jump through some hoops to deal with default entitlements / plist replacements that Xcode handles. We should either handle them or at least document some common patterns you can use to handle them yourself

Start by reviewing how this repository currently handles entitlements and plist replacements, then compare that with the defaults Xcode applies when creating an app. The issue offers two possible outcomes—supporting the behavior or documenting common workarounds—so confirm the intended scope before starting. Done should mean the selected approach covers the common patterns clearly.

Written by the indexing model from the issue text.