Make `cardinal` an optional dependency

I am currently trying to reduce to package footprint of some of my projects:

cardinal is only used in 2 places to highlight code, which in turns requires redeyed which in turn requires esprima.

I suggest either removing it from dependencies or making it an optional dependency since it is only required in debug mode, you might print a message install cardinal for pretty debug formatting or something.

[catamphetamine]

@sidorares

in the latest versions require(‘cardinal’) is wrapped in try/catch block and should not produce an error

No, still the same error with the latest 2.2.5 version.

c:/dev/JITU/node_modules/mysql2/lib/helpers.js
Module not found: Error: Can't resolve 'cardinal' in 'c:\dev\JITU\node_modules\mysql2\lib'
resolve 'cardinal' in 'c:\dev\JITU\node_modules\mysql2\lib'

cat c:\dev\JITU\node_modules\mysql2\package.json
{
  "name": "mysql2",
  "version": "2.2.5",

[sidorares]

@ashokkumarg in the latest versions require('cardinal') is wrapped in try/catch block and should not produce an error - https://github.com/sidorares/node-mysql2/blob/a640d471f043eb078c09ab0d6016030c315bd879/lib/helpers.js#L28