Add utility to sanitize and retrieve canonical github urls

Based on the work in webapp [1]

This new code is within a new arborescence as some more code will get moved alongside in a new commit (the new session github currently in swh.lister module).

Related to swh-lister#4232 (closed)

• [1] https://forge.softwareheritage.org/source/swh-web/browse/master/assets/src/utils/functions.js$118-160

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Migrated from D7836 (view on Phabricator)