Directives

[psb]

Provide a unified way to create JS directives in any part of a file using something like [@mel.directive "use client;" ].

A unified way replaces the use of [@mel.config {flags: [|"--preamble", "\"use server\";"|]}]; at the top of files and trying to use %mel.raw (e.g., [%mel.raw "'use server';"];) in the middle of files.