select_raw builds invalid syntax if not last in chain

[circulon]

Describe the bug
If using select_raw, the statement must be the last statement in the chain or the compiled query in syntactically invalid

To Reproduce

builder = (
            QueryBuilder()
                .select_raw("max(updated_at) as test").from_("some_table")
                .add_select(
                "other_test",
                lambda query: (
                    query.max("updated_at")
                        .from_("different_table")
                        .where(
                        "some_id", "=",
                        "3"
                    )
                ),
            )
        )
    
print("{}".format(builder.to_sql()))

Produces
SELECT max(updated_at) as test(SELECT MAX("different_table"."updated_at") AS updated_at FROM "different_table" WHERE "different_table"."some_id" = '?') as other_test FROM "some_table"

Which you can note there is no comma after "as test"

Expected behavior
A valid query would be generated like this

SELECT max(updated_at) as test, (SELECT MAX("different_table"."updated_at") AS updated_at FROM "different_table" WHERE "different_table"."some_id" = '?') as other_test FROM "some_table"

Desktop (please complete the following information):

• OS: Mac OSX,
• Version Catalina 10.15.7

What database are you using?

• Type: Postgres,
• Version 10.7

Additional context
Masonite-orm version 1.0.22