Add support for multiple project roots (or option to exclude sub-folders)

[troygilbert]

A config option mentioned in the docs, project_package_paths, is not available in the PHP SDK. Would be nice to support this in order to support multiple paths for app-relevant source. Another option: add a config that allows specific sub-paths of the root to be excluded, for example node_modules or vendor.

[jessicahsieh]

Internal Conversation - https://app.intercom.io/a/apps/rlisg82q/inbox/inbox/mentions/conversations/21775920029

[ArturMoczulski]

@troygilbert we will probably work on this in the upcoming quarter