Missing sound effects

Some sound effects are missing in the current version of Cambridge. These sound effects could be added as a gameplay enhancement.

- COOL!!
- REGRET!! (optional)
- Rotation (optional)
- Rotation fail (optional)
- Move fail (optional)
- T-Spin
- T-Spin Mini (optional; if T-Spin Mini sound is not set, the normal T-Spin sound effect will also play on T-Spin Mini)
- T-Spin line clears (optional; if T-Spin line clear sound is not set, the line clear and T-Spin sound effect will play at the same time)
- Hard/Sonic Drop (optional)
- Soft Drop (optional)
- Back-to-Back (optional)
- Combo (optional; the sound effects can be ranged from single to multiple, and unlike in Nullpomino, there are no number limits for combo sound effects [up to 20 in Nullpomino])
- Level up
- Grade up

Note: The sound effects marked as "optional" are meant to be not included to the Cambridge release package, but can be added through resource packs with additional audio files. The code to bypass error for missing files should be added to work around with optional files.

Start by locating the existing gameplay sound-effect definitions and resource-pack audio loading. Check how missing files are handled, then verify that the required effects play and optional effects can be omitted without errors; done means the listed effects are supported and resource packs can provide the optional files.

Written by the indexing model from the issue text.