Follow to license files in package manifest

[AyanSinhaMahapatra]

Some package manifests has attributes such as License File referencing to a license in a file. There needs to be a specific step in the license detection to determine whether we have followed this successfully. Presently this is handled generally, only if the text is matched to a rule with a referenced filename, which handles the majority of cases.
But this also needs to be done, regardless of the filename being legalese.