Add hashes.hashAllFields

stew/shims/hashes.nim

@@ -0,0 +1,10 @@
+import
+  std/[hashes, typetraits]
+
+func hashAllFields*(x: object|tuple): Hash =
+  mixin hash
+  for f in fields(x):
+    result = result !& hash(f)
+  result = !$result
+
+export hashes