Make sure directories exist for config files

[tituspijean]

cf. https://forum.yunohost.org/t/lemmy-installation-issue/27510/7

PR Status

• [x] Code finished and ready to be reviewed/tested
• [ ] The fix/enhancement were manually tested (if applicable)

Automatic tests

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[tituspijean]

!testme

[yunohost-bot]

Alrighty!