tsk-5: Add contact (#7)

Closes #5

Reviewed-on: phoenix/textsender-api#7
Co-authored-by: phoenix <kundeng00@pm.me>
Co-committed-by: phoenix <kundeng00@pm.me>

internal/version/version.go

@@ -1,7 +1,17 @@
 package version
 
+import "fmt"
+
 var (
-	Version = "dev"
-	Commit  = "none"
-	Date    = "unknown"
+	Version   = "dev"
+	BuildTime = "none"
+	Commit    = "unknown"
+	GoVersion = "unknown"
 )
+
+func String() string {
+	return fmt.Sprintf(
+		"Version: %s\nBuild Date: %s\nCommit: %s\nGo Version: %s",
+		Version, BuildTime, Commit, GoVersion,
+	)
+}