feat: support recording timestamps (#413)

Author: AlCalzone

README.md

@@ -4,7 +4,6 @@ Simple JSONL-based key-value store. Uses an append-only file to store the data.
 
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@@ -127,6 +126,10 @@ The following options exist (all optional) and can be combined:
 | `onClose` | `false` | Compress when closing the DB |
 | `onOpen` | `false` | Compress after opening the DB |
 
+### Keeping track of timestamps
+
+The DB can automatically keep track of the last time a key was accessed or modified. To do so, set the `enableTimestamps` option to `true`. Every `set` call will update the timestamp of a value, which can be retrieved using `getTimestamp(key)`.
+
 ### Import / Export
 
 Importing JSON files can be done this way: