Address pkgdown::build_site() warnings

[pbchase]

pkgdown::build_site() throws some errors. Mostly, it cannot build some of the function examples. There is also an issue with a missing dbDisconnect() call. It throws these errors:

Warning messages:
1: Failed to parse example for topic 'build_etl_job_log_df' 
2: call dbDisconnect() when finished working with a connection 
3: Failed to parse example for topic 'get_job_duration' 
4: Failed to parse example for topic 'write_error_log_entry' 
5: Failed to parse example for topic 'write_summary_metrics' 
6: Failed to parse example for topic 'write_to_sql_db' 

[pbchase]

Fixed in PR #143. Props to @ChemiKyle for hammering on the warnings