Snowflake COMMENT ON support

[psukys]

Support for https://docs.snowflake.com/en/sql-reference/sql/comment, for example:

COMMENT ON my_schema.my_table IS 'hello world'

Currently, parsing fails:

Expected: an SQL statement, found: COMMENT

[git-hulk]

Hi @psukys

I can submit a PR to resolve this issue if you're not planning to do it.

[psukys]

@git-hulk please do, I lack knowledge on internals to pick it up immediatelly