a bug is introduced in v2.0.2 defvar-local change.
the zero-input-full-width-p variable need to have a buffer local binding
when zero-input-mode is enabled. right away, not on first set.

and zero-input-toggle alias

zero-input-toggle-full-width-mode > zero-input-toggle-full-width

- dropped Package-Version metadata.
- zero-input-full-width-mode renamed to zero-input-full-width-p.
- zero-input-toggle is now an obsolete alias for zero-input-mode.
- use `defvar-local' when variable is always buffer local.
- moved test data to debug/test files.
- fixed typo. zero-input-pinin-service > `zero-input-pinyin-service'.

since this is a backward incompatible change, I set version to v2.0.0.
all symbols and functions is now prefixed with zero-input.

This change is suggested by melpa reviewer.