Undetected license file for unusual repos

[Dynnammo]

Some repos have license files named somewhat strangely : License-Agplv3.txt, etc. (cf. github.com/decidim/decidim as instance).

It would be great, instead of covering this by having a license_files list, to work followingly :

1. For GH, using the API, which itself relies on Licensee, a ruby gem that do the job pretty well : https://docs.github.com/en/rest/licenses#get-the-license-for-a-repository
2. For Bitbucket, same API endpoint does exist : https://developer.atlassian.com/server/bitbucket/rest/v804/api-group-project/#api-api-latest-projects-projectkey-repos-repositoryslug-license-get

[Mte90]

Yes, when the project started there wasn't something like this.

Ideally the actual behaviour can be a fallback in case the endpoint don't work, we should look also on GItLab if there is something similar as per #35