Create shallow-clone-object.md

We need a deep clone too but that's a different animal.

`JSON.parse(JSON.stringify(obj))` is not very good because it strips functions, etc.

snippets/shallow-clone-object.md

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+### Shallow clone object
+
+Use the object spread operator to spread the properties of the target object into the clone.
+
+```js
+const shallowClone = obj => ({ ...obj });
+/*
+const a = { x: true, y: 1 };
+const b = shallowClone(a);
+a === b -> false
+*/
+```