feat: add field filter & replace sheetId with sheetSlug

[carlbrugger]

This PR introduces an optional fieldFilter, and enables filtering by either sheetId or sheetSlug.

Example:

listener.use(autocast({ sheetId: 'us_sh_12345678' }))
listener.use(autocast({ sheetSlug: 'foo' }, ['numberField']))
listener.use(autocast({ sheetId: 'us_sh_12345678' }, ['numberField']))
listener.use(autocast({ sheetSlug: 'bar' }, ['numberField', 'dateField']))

[socket-security]

Removed dependencies detected. Learn more about Socket for GitHub ↗︎

🚮 Removed packages: @flatfile/[email protected]

[ashleygmulligan2]

Can we do the Guides docs updates at the same time?

[carlbrugger]

Can we do the Guides docs updates at the same time?

Sure thing, here it is: FlatFilers/Guides#751