Create swh-perfecthash module

Following the steps of https://docs.softwareheritage.org/devel/tutorials/add-new-package.html

• Bootstrap repository in forge (https://forge.softwareheritage.org/source/swh-perfecthash/)
• Add to swh-environment
• Add to jenkins (337d62d - checked via B24255)
• Add to docs via 56cbebe1845258ba353a2f653d3850b3c9219d5b

---

Migrated from T3634 (view on Phabricator)