make the FHIRPathParser target fully public (#98)

# make the FHIRPathParser target fully public

## ⚙️ Release Notes
- adds a `FHIRPathParser` package product


## 📚 Documentation
n/a


## ✅ Testing
n/a


### Code of Conduct & Contributing Guidelines
By creating and submitting this pull request, you agree to follow our
[Code of
Conduct](https://github.com/StanfordBDHG/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordBDHG/.github/blob/main/CONTRIBUTING.md):
- [x] I agree to follow the [Code of
Conduct](https://github.com/StanfordBDHG/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordBDHG/.github/blob/main/CONTRIBUTING.md).

Author: lukaskollmer

Package.swift

@@ -22,7 +22,8 @@ let package = Package(
     ],
     products: [
         .library(name: "ResearchKitOnFHIR", targets: ["ResearchKitOnFHIR"]),
-        .library(name: "FHIRQuestionnaires", targets: ["FHIRQuestionnaires"])
+        .library(name: "FHIRQuestionnaires", targets: ["FHIRQuestionnaires"]),
+        .library(name: "FHIRPathParser", targets: ["FHIRPathParser"])
     ],
     dependencies: [
         .package(url: "https://github.com/StanfordBDHG/ResearchKit.git", .upToNextMinor(from: "3.1.1")),