UnixSignal: Add SIGCONT (#192)

I'm using swift-service-lifecycle's UnixSignal in a text UI library, and
needed SIGCONT. It's probably not super relevant in the service use
case, but it looks like UnixSignal is the best way to handle signals,
service or not, and I don't know if there's a downside to the library
supporting it?

Author: juri

Sources/UnixSignals/UnixSignal.swift

@@ -37,6 +37,7 @@ public struct UnixSignal: Hashable, Sendable, CustomStringConvertible {
         case sigalrm
         case sigquit
         case sigwinch
+        case sigcont
     }
 
     private let wrapped: Wrapped
@@ -71,6 +72,7 @@ public struct UnixSignal: Hashable, Sendable, CustomStringConvertible {
     public static let sigalrm = Self(.sigalrm)
     /// Signal when the window is resized.
     public static let sigwinch = Self(.sigwinch)
+    public static let sigcont = Self(.sigcont)
 }
 
 extension UnixSignal.Wrapped: Hashable {}
@@ -101,6 +103,8 @@ extension UnixSignal.Wrapped: CustomStringConvertible {
             return "SIGALRM"
         case .sigwinch:
             return "SIGWINCH"
+        case .sigcont:
+            return "SIGCONT"
         }
     }
 }
@@ -130,6 +134,8 @@ extension UnixSignal.Wrapped {
             return SIGALRM
         case .sigwinch:
             return SIGWINCH
+        case .sigcont:
+            return SIGCONT
         }
     }
 }