feat(editor): Add an option to disable fullwidth toggle key

[kanru]

Fixes #487, Fixes #391

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.44%. Comparing base (0ea5400) to head (4b782a0).

Files	Patch %	Lines
capi/src/io.rs	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #605      +/-   ##
==========================================
- Coverage   89.45%   89.44%   -0.01%     
==========================================
  Files          39       39              
  Lines        8580     8586       +6     
==========================================
+ Hits         7675     7680       +5     
- Misses        905      906       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.