Add missing MySQL functions

[invisal]

Description

Function hint provides a quick document on how to use those function.

Currently, we support many MySQL functions but some are still missing such as String functions and JSON functions

• https://dev.mysql.com/doc/refman/8.0/en/string-functions.html
• https://dev.mysql.com/doc/refman/8.0/en/json-function-reference.html

How to

You can go to /dialects/mysql/functions. The function name is the file name in that folder. You can create new filename of any missing functions.

You can copy and paste from MySQL documents

• https://dev.mysql.com/doc/refman/8.0/en/string-functions.html
• https://dev.mysql.com/doc/refman/8.0/en/json-function-reference.html

Once you finish run

npm run build:dialect