shell-things/etc/pki/ca-trust/source/anchors

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Fedora & SailfishOS: drop `.pem` files of root certificates here and
`sudo update-ca-trust`.

Debian & co: drop `.crt` to `/usr/local/share/ca-certificates/extra/` (create
if doesn't exist, `/extra/` may be anything) and run
`sudo update-ca-certificates`