Issue Description:

Hi!

I hope this is not a silly question; how do you use this library inside another Swift library? I am maintaining a GraphQL client library that heavily relies on code generation. Since the code is mainly unformatted, I'd like to format it before writing it out on a disk.

I am trying to use `swift-format` (which relies on `swift-syntax`) and I am getting a strange error when using the library.

```

Undefined symbols for architecture x86_64:
"_$s11SwiftFormat0A9FormatterC13configuration16diagnosticEngineAC0aB13Configuration0G0V_0A6Syntax010DiagnosticF0CSgtcfC", referenced from:
_$sSS19SwiftGraphQLCodegenE6formatSSyKF in String+Format.swift.o
"_$s11SwiftFormat0A9FormatterC6format6source15assumingFileURL2toySS_10Foundation0H0VSgxztKs16TextOutputStreamRzlF", referenced from:
_$sSS19SwiftGraphQLCodegenE6formatSSyKF in String+Format.swift.o
"_$s11SwiftFormat0A9FormatterCMa", referenced from:
_$sSS19SwiftGraphQLCodegenE6formatSSyKF in String+Format.swift.o
"_$s24SwiftFormatConfiguration0C0VACycfC", referenced from:
_$sSS19SwiftGraphQLCodegenE6formatSSyKF in String+Format.swift.o
ld: symbol(s) not found for architecture x86_64

```

I've seen the note in swift-syntax's README that talks about linking the library, and I've found a similar issue (and its [fix|SwiftDocOrg/homebrew-formulae@af4cd47),)]), but the other libraries in the examples section in that README don't rely on any such script.

Can you help me? What am I doing wrong? What should I look at to understand the error message?

Thank you!

> I know this is not ideal, but you can find all the code in [SwiftGraphQL|https://github.com/maticzav/swift-graphql/tree/next]'s repo.