Create Dbt.gitignore

[tzing]

Reasons for making this change:

dbt generates tons of files on running, so wanna add this template for ignoring the generated files.

Links to documentation supporting these rule changes:

This template is modified from the official repo dbt-labs/dbt-utils.

I remove the venv folder from that gitignore file because it is already covered by python.gitignore.

If this is a new template:

• homepage
• github repo