documentation and other style updates

[fivetran-jamie]

Are you a current Fivetran customer?

fivetran made PR

What change(s) does this PR introduce?

• document new fields in old tables in yml and CHANGELOG
• document new tables and their fields in yml and CHANGELOG
• document deprecated fields in old tables in yml and CHANGELOG
• document new features in README and CHANGELOG
  • passthrough columns
  • postgres compat
  • timezone conversion
• identifier vars for new tables

Did you update the CHANGELOG?

• [x] Yes

Did you update the dbt_project.yml files with the version upgrade (please leverage standard semantic versioning)? (In both your main project and integration_tests)

• [ ] Yes

in base branch

Is this PR in response to a previously created Bug or Feature Request

• [ ] Yes, Issue/Feature [link bug/feature number here]
• [ ] No

How did you test the PR changes?

• [ ] Buildkite
• [ ] Local (please provide additional testing details below)

Select which warehouse(s) were used to test the PR

• [ ] BigQuery
• [ ] Redshift
• [ ] Snowflake
• [ ] Postgres
• [ ] Databricks
• [ ] Other (provide details below)

Provide an emoji that best describes your current mood

✍️ **Feedback** We are so excited you decided to contribute to the Fivetran community dbt package! We continue to work to improve the packages and would greatly appreciate your [feedback](https://www.surveymonkey.com/r/DQ7K7WW) on our existing dbt packages or what you'd like to see next.

[fivetran-jamie]

merged this into the trasnform-enhancements branch