document `jira_issue_history_buffer` variable

[fivetran-jamie]

Is there an existing issue for this?

• [X] I have searched the existing issues

Describe the issue

we have this variable for extending the history of an issue past its closing date and we don't document it anywhere!

https://github.com/fivetran/dbt_jira/blob/main/models/intermediate/field_history/int_jira__issue_calendar_spine.sql#L73

Relevant error log or model output

No response

Expected behavior

users should know it exists and how to use it

dbt Project configurations

na

Package versions

na

What database are you using dbt with?

postgres, redshift, snowflake, bigquery, databricks

dbt Version

na

Additional Context

No response

Are you willing to open a PR to help address this issue?

• [ ] Yes.
• [ ] Yes, but I will need assistance and will schedule time during our office hours for guidance
• [ ] No.