Add faq: why timestamps don't always increase

frontend/src/app/docs/api-docs/api-docs.component.html

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   <p>When a new block is found, mining pools send miners a block template with no transactions so they can start searching for the next block as soon as possible. They send a block template full of transactions right afterward, but a full block template is a bigger data transfer and takes slightly longer to reach miners.</p><p>In this intervening time, which is usually no more than 1-2 seconds, miners sometimes get lucky and find a new block using the empty block template.</p>
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+  <p>Block validation rules do not strictly require that a block's timestamp be more recent than the timestamp of the block preceding it. Without a central authority, it's impossible to know what the exact correct time is. Instead, the Bitcoin protocol requires that a block's timestamp meet certain requirements. One of those requirements is that a block's timestamp cannot be older than the median timestamp of the 12 blocks that came before it. See more details <a href="https://en.bitcoin.it/wiki/Block_timestamp" target="_blank">here</a>.</p><p>As a result, timestamps are only accurate to within an hour or so, which sometimes results in blocks with timestamps that appear out of order.</p>
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   The official mempool.space website is operated by The Mempool Open Source Project. See more information on our <a [routerLink]="['/about']">About page</a>. There are also many unofficial instances of this website operated by individual members of the Bitcoin community.
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