Add raw pulse-train callback API with documentation and example integration

[Copilot]

This change adds a user-registerable callback for raw pulse/gap trains so downstream code can consume captured RF pulse data even when no built-in decoder matches. The callback is invoked from the decoder task for every captured signal, enabling on-device custom protocol decoding without parsing serial output.

• Public API: raw pulse callback registration

  • Added rtl_433_raw_pulse_cb typedef to expose raw pulse/gap, pulse count, duration, and RSSI.
  • Added rtl_433_ESP::setRawPulsesCallback(...) to register/unregister the callback.

• Decoder pipeline wiring

  • Added internal _setRawPulsesCallback(...) plumbing.
  • Invoked the callback in rtl_433_DecoderTask after pulse data is prepared, independent of decode result (events may be zero or non-zero).

• Concurrency safety

  • Stored callback pointer as an atomic and used release/acquire semantics on registration/use to avoid cross-task races during callback updates.

• Documentation and example updates

  • Documented the callback interface and usage in README.md (including callback signature and pointer lifetime note).
  • Updated example/OOK_Receiver/OOK_Receiver.ino to register setRawPulsesCallback(...) and demonstrate raw pulse/gap logging.
  • Updated example/OOK_Receiver/README.md to note both JSON and raw pulse callback paths.

typedef void (*rtl_433_raw_pulse_cb)(
    const int* pulse_us,
    const int* gap_us,
    unsigned int num_pulses,
    unsigned long duration_us,
    int rssi
);

rf.setRawPulsesCallback(myRawPulseHandler);

[NorthernMan54]

@copilot Pls also document the interface, and create an example

[Copilot]

@copilot Pls also document the interface, and create an example

Added both in commit 22777dc.

• Documented the raw pulse callback interface and usage in README.md.
• Updated example/OOK_Receiver/OOK_Receiver.ino to register setRawPulsesCallback(...) and log sample raw pulse/gap timing data.
• Updated example/OOK_Receiver/README.md to note both callback types in the sample.