cat2151/mmlabc-to-smf-rust

AI Summary: This issue proposes to add collapsible buttons to various display fields in the demo, defaulting them to a collapsed state. The JSON result display field should be changed to a text editor, while the demo-library should remain simple.

AI Summary: This issue proposes implementing support for the special `@128` instrument in mmlabc, which signifies a General MIDI drum track. The `mmlabc-to-smf-rust` converter must assign tracks containing `@128` to MIDI channel 9 (0-based) and ensure this designation takes precedence over other instrument specifications within the same track. It also requires careful handling of program change events, which are typically ignored on drum channels, to conform to both mmlabc and General MIDI conventions.

AI Summary: This issue proposes to improve the Japanese README file by making the `grammer.js` a Single Source of Truth (SSOT). All references to `grammer.js` should be converted to clickable URLs, allowing readers to easily access and read the grammar information.