feat(spectool): Add MP3 support for audio analysis

Leverages the built-in MP3 decoder in miniaudio to allow spectool's 'analyze' command to process .mp3 files in addition to .wav files.

Updates the tool's command-line help text and the project's HOWTO.md to reflect the new capability.

1 files changed, 30 insertions, 0 deletions

diff --git a/HOWTO.md b/HOWTO.md
index afd517e..6a4d723 100644
--- a/HOWTO.md
+++ b/HOWTO.md
@@ -38,3 +38,33 @@ cd build
 ctest
 cd ..
 ```
+
+## Tools
+
+### Spectrogram Tool (`spectool`)
+
+A command-line tool for analyzing WAV and MP3 files into spectrograms and playing them back.
+
+#### Building the Tool
+
+To build `spectool`, you need to enable the `DEMO_BUILD_TOOLS` option in CMake.
+
+```bash
+cmake -S . -B build -DDEMO_BUILD_TOOLS=ON
+cmake --build build
+```
+The executable will be located at `build/spectool`.
+
+#### Usage
+
+**Analyze an audio file:**
+```bash
+./build/spectool analyze path/to/input.wav path/to/output.spec
+# or
+./build/spectool analyze path/to/input.mp3 path/to/output.spec
+```
+
+**Play a spectrogram file:**
+```bash
+./build/spectool play path/to/input.spec
+```