Include navigational memento link relations

[ibnesayeed]

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Navigational memento link relations (i.e., first, prev, next, and last) are recommended to be included in Link header of TimeGate and memento responses as many tools rely on them.

See: https://ws-dl.blogspot.com/2020/03/2020-03-26-memento-compliance-audit-of.html#1-3-main-page-memento And: https://ws-dl.blogspot.com/2020/03/2020-03-26-memento-compliance-audit-of.html#1-4-timegate