Add a new `swh lister new` command to initialize a new lister from a template

Note: there are no tests for now since I'm not 100% sure it worth the effort (or if this MR is worth merging)

(TBH I just wanted to fix the add an entry in the setup.py file part in the tutorial but my attention got caught by the rabbit...)

Jenkins job DLS/gitlab-builds #369 failed .
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• e841cfd9 - Add a new `swh lister new` command to initialize a new lister from a template

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Jenkins job DLS/gitlab-builds #370 succeeded .
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added 2 commits

• a7607abc - 1 commit from branch swh/devel:master
• 55d075af - Add a new `swh lister new` command to initialize a new lister from a template

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Jenkins job DLS/gitlab-builds #378 succeeded .
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