Fixed compiler warning about invalid file excludes in Package.swift

[Edward-Bazko]

In this PR I updated the exclude section of the Package.swift to correctly point to the license file and the example project.

Background: as a "home" directory the SPM uses <package_folder>/Sources/<package_name_folder> path format, so in our case this is: PryntTrimmerView/Sources/PryntTrimmerView/. Therefore SPM tries to find the license and example project over there, however, these items are located two levels up in fact — in the package root.

#83