Support text/plain template literals (dedent, outdent, etc)

I'm not sure how to deal with the various names this could be under (outdent is more recently updated but dedent has more weekly npm downloads, etc. while a better name might be txt similar to gql or plain as text/plain to accompany text/plain text/html, text/css, and text/javascript`) but I would like to be able to paste a block of text into my code within a tagged template and it be auto-indented prettily with the rest of my code.

Prettier 2.0.5
Playground link

--parser babel

Input:

{outdent`Hello

Goodbye`;}

{dedent`Hello

Goodbye`;}

{txt`Hello

Goodbye`;}

{plain`Hello

Goodbye`;}

Output:

{
  outdent`Hello

Goodbye`;
}

{
  dedent`Hello

Goodbye`;
}

{
  txt`Hello

Goodbye`;
}

{
  plain`Hello

Goodbye`;
}

Expected behavior:

{
  outdent`
    Hello

    Goodbye
  `;
}

{
  dedent`
    Hello

    Goodbye
  `;
}

{
  txt`
    Hello

    Goodbye
  `;
}

{
  plain`
    Hello

    Goodbye
  `;
}

Note: The best alternatives I've found is intentionally not having indentation (which I don't find pretty) or by transforming my text into arrays with things like join("\n") but neither of those are ideal:

{
  txt`\
Hello

Goodbye\
`;
}

{
  [
    "Hello",
    "",
    "Goodbye"
  ].join("\n")
}

I would be happy to author a text-tag (like graphql-tag) or a plain-literal (like html-literal) npm package to support a txt or plain tagged template if it would help (unless there's already one out there that I just haven't found yet).

Start with the linked Prettier Playground example using the Babel parser and compare the current output with the requested indentation for tagged template literals. Clarify which tag name or text/plain syntax is in scope, then use the example cases as the completion check for the chosen behavior.