Custom repo at first lime of sources.list

[fagianijunior]

This pull add the entries of Aptfile starting with :repo: to be prepended to the existing /etc/apt/sources.list, ensuring that custom repositories have higher precedence.

Changes Included:
Custom repositories are added to the beginning of /etc/apt/sources.list.

Benefits:
Custom repositories now take precedence during package resolution.
Ensures compatibility with existing repositories while enabling user-defined flexibility.

Notes:
This update preserves backward compatibility and will not affect setups without a properly configured Aptfile.

[maksimkurb]

Hello, thanks for this PR!

I am not sure that this would be backward-compatible if someone already used :repo:deb in their Aptfile, previously they were added to the end of sources.list, but now they would be always added to the front and this can break some currently working installations. So after this change custom repositories would have higher priority than original ones if users added them to their Aptfile.

It can be ok if you somehow note this change as breaking in changelog or some additional env variable could be added to control this behavior.