ld: restore module README with LibreDrive credit to Mike Chen + the MakeMKV team

src/ld/README.md

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+# ld — the LibreDrive unlocker
+
+The **LibreDrive** unlocker module for freemkv-unlock.
+
+freemkv-unlock defines the generic `Unlocker` contract; this module is one
+implementation of it. It recognizes a bundled catalog of supported drives
+(`profiles.json`) and, for a matching drive, lifts the drive-level
+bus-encryption barrier so the drive serves readable sectors. Content-key
+decryption is a separate concern, handled by the consumer.
+
+Clients never name this module directly —
+[libfreemkv](https://github.com/freemkv/libfreemkv) dispatches through
+`freemkv_unlock::all_unlockers()`, and this module answers `matches()` /
+`unlock()` when the drive identity is one it supports.
+
+## Scope: non-persistent unlock only
+
+This module performs only the **non-persistent** unlock — the access state it
+sets up lives in drive RAM and is gone on power cycle. The one-time, permanent
+drive preparation is the drive owner's own manual step and is **never**
+automated here.
+
+## Credits
+
+LibreDrive was created by **Mike Chen** and the **MakeMKV team**. This module
+builds on their work — our thanks and full credit to them for the LibreDrive
+capabilities.