Add `.sh` tool to load database dump

[MizukiTemma]

Short description

It seems we will need more and more often testing with database dump, so I would like to share this small tool I made after forgetting how to do it and comming back to the instruction again and again.

Proposed changes

• Gather all the steps in this instruction

• Use it just like other tools with the path to the extracted SQL data. Ex: ./tools/load_database_dump.sh ../integreat-2024-05-25.sql

Side effects

• The error rm: cannot remove '/home/xxxxxxx/integreat-cms/.postgres/data': Permission denied will appear. You can just use sudo rm -r .postgres/data. If you know how to overcome this inconvenience, let me know please in the review 👀
• I'm not familier with thema Docker etc and not sure whether this tool can work in others' environment.

Resolved issues

Fixes: #

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