Using HashCode in .NETFramework

How to use HashCode type in full .NET, which doesn't support it
So, I just learned that not even in .net472/net48, you can leverage the cool HashCode type from .NETCore. It is mentioned in docs as available in ".NET Platform Extensions 3.1", which isn't quite clear what it means. After a quick search here and there, I found out the Microsoft.Bcl.HashCode package, which seems to be one such ".NET platform extension" (although the version # doesn't match either :/).
With that, I can now make a KeyValuePairComparer<TKey, TValue>to check for dictionaries equality like:
public class KeyValuePairComparer<TKey, TValue> : IEqualityComparer<KeyValuePair<TKey, TValue>>
public static KeyValuePairComparer<TKey, TValue> Default { get;} = new KeyValuePairComparer<TKey, TValue>();
public bool Equals(KeyValuePair<TKey, TValue> x, KeyValuePair<TKey, TValue> y) => object.Equals(x.Key, y.Key) && object.Equals(x.Value, y.Value);
public int GetHashCode(KeyValuePair<TKey, TValue> obj) => HashCode.Combine(obj.Key, obj.Value);
To be used as:
IReadOnlyDictionary<string, string> first = ...
IReadOnlyDictionary<string, string> second = ...
return first.SequenceEquals(second, KeyValuePairComparer<string, string>.Default);