Reorganize files in project

...e/example-app/Sources/LandingFeature/LandingFeature.swift

Example/example-app/Sources/LandingFeature/LandingView.swift

...e/example-app/Sources/SessionFeature/SessionFeature.swift

Example/example-app/Sources/SessionFeature/SessionView.swift

...e/example-app/Tests/AppFeatureTests/AppFeatureTests.swift

...ample-app/Tests/ErrorFeatureTests/ErrorFeatureTests.swift

...e-app/Tests/LandingFeatureTests/LandingFeatureTests.swift

...e-app/Tests/SessionFeatureTests/SessionFeatureTests.swift