Support files.include from .denolint.json

[prantlf]

Complete the existing support of files.exclude.

Once files.include is provided, the current directory will not be added to the source directories by default.

BREAKING CHANGE: If you used files.include in your .denolint.json to list a subset of the subdirectories, but you expected denolint to search all subdirectories in the current directory, this will not happen any more. If you use a config file with files.include, only directories listed by files.include will be searched.

Attempts to fix #635.