Support Yams 5.0 (support 4.0.0 ..< 6.0.0) (#111)

### Motivation

We're not on the latest major version of Yams, which blocks adopters
updating
their dependency on Yams. But since updating is cheap (we're not using
any of
the APIs that have changed in the latest release) we can upgrade to
allow
dependency resolution for others.

### Modifications

- Update dependency on Yams to 5.0.0.

### Result

- Unblocks adopters wishing to use Yams >= 5.0.0.

### Test Plan

CI.

Author: simonjbeaumont

Package.swift

@@ -56,7 +56,7 @@ let package = Package(
         ),
         .package(
             url: "https://github.com/jpsim/Yams.git",
-            from: "4.0.0"
+            "4.0.0"..<"6.0.0"
         ),
 
         // CLI Tool