[Tests] Add test coverage documents for Reference<T> class

[JckXia]

class	methods
Reference	Reference()
	Reference(napi_env env, napi_ref ref)
Covered #212	Reference::New(const T& value, uint32_t initRefCount = 0)
	Reference(Reference&& other)
	Reference & operator = (Reference && other)
	Env() const;
Covered #702	bool IsEmpty() const
	bool operator == (const Reference& other) const
	bool operator != (const Reference& other) const
Covered #212	T Value() const
Covered #212	uint32_t Ref()
Covered #212	uint32_t UnRef()
	void Reset()
	void Reset(const T& value, uint32_t refCount = 0)

[github-actions]

This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.

[github-actions]

This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.

[github-actions]

This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.

[github-actions]

This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.

[legendecas]

Closed by #1277