Support Composer 2.9.0 Automatic Security Blocking

[AlexSkrypnyk]

Composer 2.9 added automated security blocking when installing or updating packages.

For backwards compatiblity, we need to disable this in root composer.json with:

"config":{
        "audit": {
            "abandoned": "report",
            "block-insecure": true
        },
}

We also need to update the Composer section in the Vortex own docs (.vortex/docs) to describe:

1. The new composer behaviour
2. The possible values this can take and how to decide which option to use as a site owner

We need to update docs/faqs.md to include a short message about what to do when a security blocking does not allow to install packages and link it to the Vortex composer page.