Create alasql.d.ts
Create alasql.d.ts

https://github.com/agershun/alasql/issues/428 stated that this file is no longer in dist 

was removed at https://github.com/agershun/alasql/commit/7c3f2c81b7fccc9e6bd1c8abfe86623207beb979

but is never generated when we build from `src/`
kanghj/alasql,agershun/alasql,agershun/alasql,kanghj/alasql,agershun/alasql,kanghj/alasql,agershun/alasql