Useful sed
tester - https://sed.js.org#
Find all image links
ag -c '!\['
Convert image links (with quoted titles)
sed -i -r 's/!\[(.*)\]\((.*) "(.*)"\)/{{< screenshot "\2" >}}\3{{< \/screenshot >}}/g' file.md
Convert document links to short codes
[title](../path/other.md#anchor "title") => [title]({{< relref "../path/other.md#anchor" >}})
sed -i --regexp-extended 's/\]\(([^)]+\.md(#[^")]+)?)( "[^"]+")?\)/]({{< relref "\1" >}})/g' file.md