Add Brotli Test Files

[midnight-dev]

Just added some shell files and the files inside /testdata/ so users can test brotli-specific features. This also fixes the warnings output when VS / CMake expects to find missing files (like alice29.txt).

Not all of these files are strictly required, so it can be trimmed down to just the necessities if needed.

For future reference, these files were missing from the generated & tagged zip downloads of the google/brotli codebase, but cloning the repo did the trick.