Poor documentation about `sql.database` config field.

[ynn]

Currently, README.md says

• sql.database: Choose the database syntax flavor, default to guess

but it lacks information such as

• What kind of values are accepted?

• What is guess? What kind of algorithm is used to guess the database?

• If the guessing algorithm fails, to what database it falls back?

The answers to all of these questions are found in utils.ts.

Currently I have no time to create a PR, but it would be great if README.md contained these critical information.

[Heyward Fann]

coc-sql/package.json

Lines 46 to 57 in 46f4579

 "sql.database": { 
   "type": "string", 
   "default": "guess", 
   "enum": [ 
     "db2", 
     "hive", 
     "mysql", 
     "mariadb", 
     "bigquery", 
     "postgresql", 
     "transactsql" 
   ],